Contents

Cover

Title Page

Warhammer 40,000

Prologue

Chapter One

Chapter Two

Chapter Three

Chapter Four

Chapter Five

Chapter Six

Chapter Seven

Chapter Eight

Chapter Nine

Epilogue

About the Author

A Black Library Publication

Warhammer 40,000

It is the 41st millennium. For more than a hundred centuries the Emperor has sat immobile on the Golden Throne of Earth. He is the master of mankind by the will of the gods, and master of a million worlds by the might of his inexhaustible armies. He is a rotting carcass writhing invisibly with power from the Dark Age of Technology. He is the Carrion Lord of the Imperium for whom a thousand souls are sacrificed every day, so that he may never truly die.

Yet even in his deathless state, the Emperor continues his eternal vigilance. Mighty battlefleets cross the daemon-infested miasma of the warp, the only route between distant stars, their way lit by the Astronomican, the psychic manifestation of the Emperor’s will. Vast armies give battle in his name on uncounted worlds. Greatest amongst His soldiers are the Adeptus Astartes, the Space Marines, bio-engineered super-warriors. Their comrades in arms are legion: the Astra Militarum and countless planetary defence forces, the ever-vigilant Inquisition and the tech-priests of the Adeptus Mechanicus to name only a few. But for all their multitudes, they are barely enough to hold off the ever-present threat from aliens, heretics, mutants – and worse.

To be a man in such times is to be one amongst untold billions. It is to live in the cruellest and most bloody regime imaginable. These are the tales of those times. Forget the power of technology and science, for so much has been forgotten, never to be re-learned. Forget the promise of progress and understanding, for in the grim dark future there is only war. There is no peace amongst the stars, only an eternity of carnage and slaughter, and the laughter of thirsting gods.

Prologue

It was just as the second sun of Macragge set over the polar fortress that the alarms sounded. Here, far from the planet’s capital and the main structure of the Ultramarines’ fortress-monastery, the siren blared throughout empty halls and antechambers. In response, several medical servitors came clattering up the stone steps leading to the meditation chamber.

The servitors broke the seal on the chamber door and entered. Inside, it looked like a hurricane had struck. Ancient, heavy volumes that once lined the walls had been picked up and hurled by a tremendous explosion of energy, and now lay scattered around the chamber with crumpled spines and tattered bindings. Amidst hundreds of torn paper scraps denoting warp symbolism and meditation techniques lay a gigantic human form. Blood dripped from the giant’s eyes and nose, pooling on the hard stone floor and staining yellow parchment a sickly brown. Though the figure was out of armour the servitor orderlies still struggled to turn him over to check his life signs.

‘Back!’ came a bellowing voice from outside the chamber. The servitors reacted instantly, for they were programmed to treat the voice with the same awe and respect that a human would. It was a voice that held the greatest authority on the world of Macragge, save perhaps for that of Lord Marneus Calgar himself. The servitors scurried into the corners of the meditation chamber and Chaplain Ortan Cassius entered.

He wore his armour – even away from battle during the everyday business of the Chapter, Cassius was rarely out of it – but eschewed the skull-faced helm typically worn by Chaplains. In its place was something just as fearsome, for xenos acid had stripped away half of his face. He had never had the muscle and skin replaced, wearing his mutilation not as a badge of honour but as a reminder of how any of them could fall. The bionic eye set into the bare socket whirred faintly as it swept around the chamber, taking in the scene.

Cassius kneeled beside the fallen figure. ‘Brother Tigurius,’ he said. ‘What has happened to you?’

The Chaplain nodded at one of the servitors and it came forward, drew an auto-injector and slid the needle into an interface port on Tigurius’ forearm. His body tensed as the cocktail of stimulants flooded through his system, the huge dose tailored to a Space Marine’s immense constitution.

Tigurius gasped and his bloodshot eyes opened, unfocused and confused. Cassius helped him into a seated position and he regained some semblance of the composure befitting the Chief Librarian of the Ultramarines.

The alarms died down as the chamber’s life sign sensor returned its readings to normal.

‘What ails you, brother? What have you seen?’ asked Cassius.

‘Madness,’ breathed Tigurius.

Cassius helped the Chief Librarian to his feet. The two Space Marines were of similar height, but Cassius seemed to dwarf Tigurius both with the bulk of his black-painted armour and his presence alone. Tigurius exuded wisdom and calm, while a barely-suppressed fury bled from the Chaplain, the potential for rage and violence stated with every glance and movement.

‘What laid you low, brother?’ asked Cassius, anxiously. ‘Are we attacked?’

‘I came here to meditate,’ the Chief Librarian whispered hoarsely. ‘To cleanse my mind and soul. Instead the warp rushed into my dreaming consciousness, an endless torrent of nightmares echoing inside my skull.’

Tigurius paused.

‘I saw something stir,’ he said. ‘A nameless dread from the darkest days of our Chapter. It is loose in realspace once more, devouring, consuming. Millions have fallen. I saw them all, drowned by the swarm. Fodder for the host.’

Cassius’ half-ruined visage was not capable of so subtle an emotion as concern, but worry crept into his iron tones. ‘Kraken? Has the hive fleet returned?’ he asked.

‘It looked back,’ Tigurius said. ‘I reached out to touch it, and it looked back.’

The Chaplain understood just how close Tigurius had come to obliteration. If one valued their mind, they did not attempt to scry on the unknowable horrors of the tyranid hive mind. Some had attempted it; they had all died, their consciousnesses annihilated by the immense mental feedback from an intelligence comprising countless trillions of inhuman organisms.

‘They have returned,’ whispered the Chief Librarian.

Tigurius crossed the chamber and threw open the doors leading to the meditation chamber’s balcony. The chill wind of Macragge’s northern pole blew in, sending scraps of parchment fluttering across the room. The meditation chamber was at the top of one of the fortress’ towers, and in the chill, clear day the view stretched for hundreds of miles. The polar mountains looked like a churning grey sea frozen in a storm, the peaks of the waves capped with snow that never melted. The shadow of the fortress’ orbital defence lasers fell across mountain slopes scarred with acid and pockmarked with artillery shells. The scree was scattered with heaps of alien skulls marking where mighty sons of Ultramar had fallen a generation ago, when an endless swarm of xenos organisms had spread across that stone expanse like a voracious infection.

‘They have returned,’ echoed Cassius. ‘Who are “they”?’

Tigurius took a deep breath, letting the cold, cleansing air rush into his lungs. Then he turned back to the Chaplain.

‘I cannot know, exactly,’ he admitted. ‘Two years ago, when we broke the back of Kraken, the aliens’ bio-vessels fled in a hundred directions, slipping back into the warp or disappearing into dark space too dangerous for us to follow. The hunger I sensed could originate from any one tendril of their hive fleet. Or it could be a harbinger of some new dread set to be unleashed across the galaxy.’

He raised a palm, and clutched his eye. His hand came away red.

‘This thing, it knows us,’ he whispered. ‘It is a nightmare I–’

‘Where is it?’ said Cassius.

Tigurius showed no umbrage at the interruption. ‘Close,’ he said. ‘Too close. There were familiar images buried in the madness. I saw the forges of the Machine God, and planets bathed in yellow, toxic sunlight. I fell through the drifting gas-fields of an hourglass nebula the colour of burning promethium, and came to rest under the glare of a fading star.’

He closed his eyes. ‘The sun and the nebula. I have seen them before. They lie at the edge of the Ultima Segmentum beyond the Maelstrom.’

‘At the gates of the Segmentum Solar? Ryza lies there, as do dozens of other worlds under the control of the Adeptus Mechanicus. How in the primarch’s name could they have missed this?’

‘The Adeptus Mechanicus obsess over their own mysteries, while the galaxy moves on around them,’ said Tigurius.

‘The whole Aurus sub-sector could fall,’ said Cassius.

‘Would that I could say otherwise. We should consult with Lord Calgar immediately. We must also make contact with the Mechanicus. Come.’

The Chief Librarian pushed open the doors of the meditation chamber, and together the Space Marines strode down the steps and out into a long, vaulted hallway.

‘The Ultramarines must respond,’ said Cassius as they went. ‘An overwhelming force must be assembled to crush this threat quickly. Do you not agree?’

‘If I said no,’ said Tigurius with a weary half-smile, ‘would you listen, Lord Chaplain?’

Chapter One

The engines screamed and the world called Kolovan screamed back, the howl of a toxic storm that roared and scraped at the lower hull of the drop pod. Cassius knew the violent sensations of a drop pod assault intimately: the chill wail of the thin upper atmosphere, the hammering of the retro jets firing up, the hiss and buffet as the pod punched down through cloud cover and the rising bellow of the jets fighting against the thickening air.

As the pod screeched into its final descent attitude, these sensations were as familiar as taking a breath. Leaning into the pod’s lurches was like taking a step or speaking a word.

‘Clear your minds, brethren,’ said Cassius, trusting in the amplified vox-channel to carry his voice above the storm of the descent. ‘Seize upon only that symbol that shall lead you to victory. The sacrifice of Lord Guilliman. A passage from the Codex. The sight of blessed Macragge from space. An emblem of all we fight for. Take it and focus on it, and your soul shall be ready for the fight. Be pure and steel-hearted! Be all that is fury and righteousness!’

He was making his descent to the surface alongside a Tactical squad from the Third Company. Sergeant Verigar led them, a grey-haired veteran whose temple and left cheek glinted with the dull sheen of bionics. For now his stern visage was hidden beneath the pitiless iron mask of his red Mark VII helmet, and he sat with the easy calm of a warrior who had been through dozens, hundreds, of landings like this. Cassius had not fought beside Verigar before, but Captain Fabian spoke highly of him. He knew the names and faces of the others, but had not yet ascribed particular value to any of them. He would see them fight, and then he would know them.

The grav-restraints tightened and forced Cassius back into the plasteel frame holding his armoured body in place. A moment later the drop pod slammed into the ground. The retro engines and shock absorbers did not completely cancel out the teeth-rattling impact, and Cassius’ head snapped back and forth with the force.

The restraint around Cassius’ right arm snapped free. The Chaplain drew his crozius arcanum from its compartment at his side.

He was armed. He was ready to kill.

The explosive bolts in the drop pod’s upper hull fired like a series of gunshots. Light blared in as the hull split into four sections and fell away, exposing the Space Marines inside to the sun of Kolovan for the first time.

The star that hovered overhead and shone between clouds of filthy brown toxins was a painful, acid yellow. It fell on a broken plain, as if the surface had been baked hard by that sun and then shattered by a vast hammer. Deep fissures broke the land up into patches of scorched ground, and fingers of pale rock broke through, the bones of the planet, where the ground had been particularly tortured. A distant line of smouldering mountains spoke of the geological activity that had torn this place up over and over again.

More drop pods bearing the colours of the Third and Fifth Companies were thudding home, raising splintering showers of broken earth. As the crafts’ bolts fired, squads of Ultramarines leapt out, weapons raised and ready to kill, the blue of their armour discoloured by the sickly filter of Kolovan’s sun.

Cassius’ grav-restraints snapped open, and he jumped from the drop pod as his men disembarked alongside him. A thousand battles’ worth of experience flooded through him and he took a tally of the landscape around him in the space of a few seconds.

Broken ground, difficult to move over swiftly. Rises and breaks in the earth could serve as cover. The rest of the strike force was making landfall closely-grouped, for the crew of the ship Defence of Talassar had performed their task well in launching the drop pods from upper orbit.

The air was toxic. It would have dropped a normal man in a couple of minutes. A Space Marine’s constitution could survive it initially but it would build up over time, and so Cassius wore a rebreather unit over his mouth and nose. The toxins stung the skin that still remained on his blasted face, the wind that carried them sharp with the dirt whipped up by the drop pod’s impact.

‘We’re east of the drop zone!’ came a vox on the command channel from Captain Galenus of the Fifth Company. ‘The xenos are massing from the south.’

‘Sigillite’s teeth,’ swore Captain Fabian of the Third over the vox. ‘We expected no resistance here.’

‘Do I detect dismay, brother-captain?’ said Cassius. ‘This is but a drop in the ocean compared to what will come. Let the men test their fury. It will do them good.’

Cassius turned to the battle-brothers emerging from the drop pod. ‘The tyranids were not so distant as we feared,’ he said. ‘They mass and respond from the south. We take the southern ridge, and we hold it until our main force makes landfall.’

His squad nodded gravely. Gauntleted fingers rested on weapon studs. Blades were checked and stowed. They were ready.

‘We hold the ridge,’ Cassius repeated through the vox. ‘Fabian, you are with me. Captain Galenus, take position to the east and be wary of flanking attacks. Let them come in their thousands, and let them feel the wrath of Guilliman’s sons. We are the wall against which the enemy will break.’

‘Move out,’ growled Sergeant Verigar, wisely leaving the oratory to his Chaplain.

‘Let us send the foul xenos shrieking into the abyss,’ roared Brother Ortius, doing the opposite.

Cassius let it pass. He knew what strength the expression of battle-joy gave them, and he knew what it covered up. Like everything else, it was there to be used by leaders like Cassius, turned into another weapon in the arsenal of the Ultramarines.

Other squads from Third Company joined with his own, while the landing forces of the Fifth secured the eastern edge of the ridge – Tactical squads, standing tall and proud in their burnished warplate, ready to face the enemy with a torrent of bolter fire; Assault Marines, chainswords already roaring with eager fury; and Devastator squads wielding pristine plasma cannons, missile launchers and heavy flamers. The latter would be key, Cassius knew; disciplined bolter drill and skilful bladework had their place in any battle, but against the swirling, writhing horror of a tyranid swarm, a swathe of cleansing flame or a sanctified warhead engraved with holy rites and packed with refined explosives were often the more effective countermeasures.

Cassius ran up the ridge of broken earth to the south of the drop pod site. As he crested it he saw the land reached down into a shallow depression where once an ancient river had fed a lake now long-drained by the land’s upheaval. Into that bowl flowed not water but a mass of chittering, scrabbling flesh, a thousand limbs, the acidic sun gleaming on glossy carapaces and glinting on rows of sharp teeth.

Tyranid battle-organisms, numbering in the hundreds. They were termagants and hormagaunts, creatures evolved to serve as the foot soldiers of the hive mind, to swarm in massive numbers and flood the battlefield with gnashing teeth. Towering over them were a dozen warrior-forms that stalked on their two hind legs and lashed at the smaller creatures with whips of living flesh. The tyranids of each hive fleet had their own appearance and colouration, and these specimens had a particularly ill look to them – maggot-pale skin and plates of ivory exoskeletal armour, with eyes as black as night and maws full of glinting white teeth.

There were two options. The first was to wait at the ridge for the tyranids to reach the Ultramarines, withering their numbers with bolter fire. The second was to advance to meet them and fight them face to face, driving a wedge of power-armoured fury into the heart of the aliens.

Cassius’ role as a Chaplain, as a custodian of his brothers’ souls and an example of the Space Marines’ fury in battle, screamed to opt for the latter approach. His hatred was a physical ache as he looked upon the foe, and every fibre of his being was dragging him down off that ridge and into their roiling midst.

No. There would be time enough for that later. For now, the landing zone must be secured. The Codex, the word of Guilliman, willed it, and so he waited. He waited until the foul creatures skittered heedlessly into the effective range of the Ultramarines’ bolters.

‘Volley fire,’ yelled Cassius, brandishing his crozius arcanum above his head. ‘Burn this filth to cinders. For Macragge! For Mankind! For the Emperor!’

The Third Company Ultramarines opened fire, and a wave of mass-reactive death rolled over the front of the advancing horde. The hissing shriek of the advancing bio-organisms was drowned in an explosion of sacred ammunition that burst carapaces, split leering skulls and sent up a cloud of ichor so thick that it obscured the back of the swarm. It did not matter. From their elevated position, and with such a wealth of targets, the Ultramarines simply could not miss. Heavy bolters bellowed as they tore great rents in the enemy line, and smoking contrails marked the passage of missiles that impacted in the thickest patches of tyranids, erupting in great gouts of orange flame and sending clouds of gore and chitin whipping through the air.

Still they came on. A storm of fire that would have broken the back of any regular force could not force the tyranids into retreat. These creatures were bred only to die and to kill, and fear was a mortal concept that simply could not be applied to whatever vile consciousness urged them forward. Each war-organism was perfectly adapted to its battlefield role, and while the hormagaunts were evolved to leap and slash with the huge claws on their forelegs, the more numerous termagants had forelimbs adapted to wield symbiotic organisms as missile weapons. Through the torrent of bolter rounds that bracketed the dustbowl, dozens of termagants scuttled forward with their fleshborers raised and a hail of biological rounds erupted from the firing orifices.

Cassius dropped a shoulder to take the incoming fire on his shoulder guard. Burrowing beetles thudded into his armour as he ran, the tiny creatures expending their short lifespans in chewing through their target. The ceramite of Cassius’ armour held and the beetles fell away as the bipedal warriors roared and the hormagaunts loped to the fore. Shrieking and hissing, they clawed their way up the rise and towards the Ultramarines.

Cassius brought his combi-bolter up and fired into the clutch of hormagaunts leaping towards him. They were so fast they could cover the ground from long bolter range to close combat more quickly than most soldiers could bring their weapons to bear. Cassius was ready for them and he felt the familiar kick of the combi-bolter in his hand as he sent the volley of shots into the tyranids. Two fell, tumbling beneath the hooves of the xenos behind them.

With a flick of his thumb Cassius switched firing modes. The next time he pulled the trigger, a gout of fire spurted from the underbarrel flamer nozzle. Another hormagaunt was wreathed in burning fuel and collapsed in a heap, shrieking and spasming as its muscles burned away.

Another group of tyranids had made the ridge, and were dismembering an Ultramarine with wicked swipes of their scythed boneblades. Cassius met them with a bellow of fury and a swing of his crozius. He aimed his holy weapon at a warrior-organism looking up from the dead Space Marine, gobbets of flesh and splatters of blood slathered across its vile maw. The xenos seemed to move in slow motion as the upward arc of Cassius’ crozius shattered its twin foreclaws. Screeching, the hormagaunt slammed into Cassius, but he threw it to the ground, putting a bolter round through its skull as it writhed in the dirt.

He risked a glance down the line. The Third were butchering the enemy with the same furious enthusiasm on every side. Sergeant Verigar rammed his chainblade into the throat of a creature that tried to slash at him, hauling it into the air and firing three rounds into its torso with his bolt pistol. Brother Estus laid down wicked bursts of covering fire while Brother Olian primed and rolled a frag grenade down the ridge. Cassius did not see what it hit, but he heard the wet thud of its detonation, and felt a rain of dry earth and rancid biological matter splatter across the side of his face. He almost smiled.

A group of termagants scuttled out of the pack to the squad’s right, trying to sweep around them and launch fleshborer volleys into them from behind. They were met by a storm of bolter fire from the battle-brothers of the Third Company. Captain Fabian directed his squads into position as they hammered volley after volley into the tyranids. His blade was slick with alien blood, and he raised it in salute to the Chaplain before spinning to unleash a torrent of energy from his plasma pistol, the white-hot bolts of flame enveloping a trio of warrior-organisms and burning them to nothing in an instant.

‘We deny them!’ yelled Cassius. ‘We wet the desert with their foul blood!’

Brother Morvion crashed into a hormagaunt a few steps from Cassius, bowling the creature onto its back legs with the weight of his armoured body.

Morvion snarled as he rammed his combat knife through the hormagaunt’s throat. ‘Die,’ he spat. ‘Die!’ He had lost his grip on his bolter, but was using his weight to pin the creature down as he punched and stamped on its skull, cracking its chitin plating and dousing himself in sickly pale fluid as he jerked his blade back and forth.

‘Morvion!’ roared Cassius. ‘Kill the damned thing and recover your weapon.’

The Chaplain marked the Space Marine’s name for censure. Ultramarines did not abandon their weapons and ignore a tactical advantage to brawl with the enemy like some hive ganger.

Cassius waded through the tyranids, batting aside one hormagaunt and letting Morvion fend off another. Above the sea of snapping teeth and claws loomed the shape of the closest warrior-form, twice the height of a Space Marine, wielding twin bone blades with one pair of forearms and a long-barrelled weapon of flesh and bone with the other.

The tyranid warrior saw Cassius approaching. Its deep-set black eyes, like flecks of obsidian set into its face, focused on him. Like its swarming cousins, the thing was an anaemic yellow-white streaked with veins of cancerous black. It raised its weapon and the end of the barrel snarled like a mouth, a spiny tongue slavering between its fleshy lips. The bulbous gland at the base of the barrel flared and the weapon belched a mass of thorny vine-like tendons that slammed into Cassius.

The thorns twined around him and constricted as he tried to move. Cassius ripped an arm free and let the crozius’ power field discharge. The power weapon shredded the vines and he was free, kicking his way out to close the distance with the warrior.

There was a symbolism to war that every Chaplain had etched on his memory. Just as a commander had to know the tactical lore of the Codex Astartes and the lessons of the Chapter’s combat histories, a Chaplain had to know the images and sensations that would drive his battle-brothers on to greater fury, steadfastness or pride. A Chaplain had to become such an image himself; when Cassius stood at the pulpit and spoke the words of the Codex or of the great deeds of Lord Guilliman and heroes of the Chapter, he became like a stained-glass window or a statue, an illustration of the Ultramarines’ ideals. When he delivered admonishment to brothers who had been lax in their duties, he became the face of the primarch himself, his face hidden by the skull mask of his rank or Cassius’ own mask of scar tissue and bone.

And in the thick of battle, when the Ultramarines needed a symbol of fury and relentlessness, Cassius became that symbol. His battle-brothers saw him as he leapt at the tyranid warrior, within the arc of its strangler cannon and into the sweep of its twin boneswords.

Cassius’ combi-flamer, Infernus, blasted a sheet of liquid flame up into the warrior as it loomed down over him. The alien screeched as fire billowed up around it and muscle blackened and shrivelled away. Cassius followed up with a low blow at the creature’s hindleg and, with a satisfying crunch, the head of the weapon smashed through the chitin of the warrior’s exoskeleton and through into the pulp of muscle and tissue.

The tyranid warrior dropped to one knee. It lost none of its speed and Cassius barely parried the bonesword that lashed at his head. The second strike caught him a glancing blow on his left shoulder spinning him around and forcing him to throw the crozius into a desperate guard as the first blade came down at him again. Suddenly the creature rocked to the side, and the weapon-limb aimed at his head instead cracked into the ground as the alien fought for balance.

Eight Ultramarines stood their ground, pouring a vicious hail of fire into the towering creature. Cassius’ heart surged with pride as he saw the newcomers. Each wore the symbol of a skewered tyranid skull on his right shoulder-plate, and the armour of each was littered with honour scrolls which fluttered in the toxic wind. Their helms were painted the white of combat veterans, and the accuracy of their onslaught proved the truth of this accolade – these men had been tempered in the hellish nightmare of the Tyrannic Wars, and they knew their business well. The warrior-organism howled. Its bony armour plating was not simply blasted and scarred by the assault – smoke rose from ruptured flesh, as the specialised bio-acid embedded in each bolter round began to devour the creature’s innards.

Wracked with agony, the xenos turned to face this new threat, forgetting Cassius for just a moment to bring its strangler cannon around.

Cassius leapt up, firing two shots into the underside of its skull as he brought the crozius around in an overhand strike. Its power field had recharged, and it erupted now. The armour covering the warrior’s sternum split and Cassius buried the head of the weapon deep in its chest. The warrior spasmed as Cassius held it there for a moment, anchored in place by the crozius’ ornate eagle wings hooked into its flesh. The arms carrying its boneswords flailed aimlessly and fell limp. The weapon came loose and the warrior pitched over, showering gore from its ruptured chest.

‘So will it be for all your wretched kind,’ muttered Cassius. He raised his crozius again, and brought it down on the tyranid’s skull, which burst into wet fragments of bone.

The Tyrannic War veterans nodded at Cassius in appreciation of the kill, before reloading their hellfire-round magazines and turning away to seek new targets. One remained, marked out by the black of his armour, which matched the Chaplain’s own. Upon his shoulder he wore not the inverted omega symbol of the Ultramarines, but a pair of crossed scythes, painted in the same acid yellow of Kolovan’s sun.

‘Chaplain,’ he said, his voice a dour growl.

‘Sergeant Remas,’ Cassius replied. The sergeant gave an almost imperceptible nod, and strode off after his men.

The Ordo Xenos of the Inquisition, the magos biologis and the strategoes of the Astra Militarum had all collected reams of data on the tyranids. It was an endless task, for the tyranids evolved to counter every tactic used against them and new variants on the hive fleets’ base organisms turned up every time the Imperium clashed with the aliens. But some constants remained. The lesser organisms, the variants on the termagant form, possessed only the capacity to act on crude animal instincts. To act in concert, as an army, they needed a directing force, which for the tyranids came in the form of leader organisms that transmitted the directions of the hive mind.

The warrior-form Cassius had just killed was one such organism, and without it the tyranids nearby lost their focus. They snapped and charged at random instead of surging in waves. Some fled or tried to burrow into the broken ground instead of fighting. The Third Company opened up a great, bloody rift in the tyranid mass in Cassius’ wake, hammering the lesser organisms back with bolter fire and isolating and butchering them in ones and twos. Brother Covellos vaporised panicking knots of termagants with space-warping blasts of his grav-cannon. Warrior organisms writhed on the ground as they fell over one another to flee or counter-charge, and were despatched on the ground.

Cassius jumped up onto the command-beast’s ruined corpse, giving him another metre of vantage point so he could see all the way back to the battle-brothers of the Fifth Company in their firing lines to the east. They had reaped a toll no less catastrophic on the enemy’s left flank. Wretched, torn corpses littered the ground in front of their position like a sea of crushed maggots. Cassius held up his blessed crozius, still splattered with gore from the dead creature’s skull. He stood triumphant on the corpse of his enemy, and roared his victory to the tortured sky. His exultation echoed through the vox and into the ear of every Ultramarine on the field.

‘Victory! We have victory! For Macragge! For the Golden Throne!’

All eyes went to him. He was a symbol of triumph, of destruction, of how the greatest of the tyranids were just fodder beneath the Ultramarines’ assault – a symbol of the victory demanded by the legacy of Roboute Guilliman.

Cassius understood the power of such symbols like few others. Creating and nurturing them was his purpose as a Chaplain. It was with such an image in their hearts that the Ultramarines would scour the tyranids from Kolovan.

Chapter Two

The automatic guns of the Ultramarines’ defences tracked across the broken land as their sensors searched for the tell-tale signals of tyranid body heat. The aliens’ metabolisms were many times faster than a human’s and their heat signatures were similarly bright, and here and there a tyranid organism emerged from its skulking place in the earth to be shot down by a blast of cogitator-aimed heavy bolter fire.

The Ultramarines landing zone was established before nightfall. The Third and Fifth Companies, having exterminated the tyranids infesting the immediate vicinity, had drawn back and fortified the zone as the strike force consolidated its first foothold on Kolovan. The first drops from the Defence of Talassar overhead had been the sentry guns and a few Rhinos and Land Speeder scouting vehicles. The rest of the strike force’s vehicles remained on the cruiser, for the foothold was still in danger of being overrun before the Ultramarines fully consolidated their grip on the planet.

‘As the sun sets,’ said Cassius, addressing the assembled brethren of the Third and Fifth Companies, ‘so do the hopes of this world. The xenos have taken their piece of flesh from Kolovan. Many of its cities have fallen and the populace has been culled. And yet the Ultramarines will place their lives upon the altar of battle, at the mercy of fate. For we understand what is truly at stake on this world.

‘With Kolovan’s fall, the hive fleet shall drain it of its biomass and, thus swelled, will surely move on to Ryza. And Ryza, already fighting the greenskins and unable to defend itself against an assault by the tyranids, will surely fall in turn. As Ryza falls, the hive fleet will open the gates to the Segmentum Solar. Hive Fleet Kraken will have a way into the heartland of the Imperium, the Sol System, Holy Terra itself. But all of these things exist in a future that will never come to be, for it is on Kolovan that the Ultramarines will halt the hive fleet.

‘It is on Kolovan we will avenge every death the xenos have inflicted, and have yet to inflict. Though the tyranid does not feel emotions as we do, know that it will feel despair when its hope of threatening the beating heart of the Imperium is blunted here. It is fear it will know to witness the Ultramarines undoing its grand gambit, and it will know hatred as we drive it from this world with blade and bolter. These things we will teach it, my brothers! For as we shall know no fear, we shall bring fear to that which has never known it!’

The sermon carried far in the cold, still air of the night. By day the desert was baked by the cruel sun, but by night it bled all its heat out into a clear sky and became chill enough to kill an unprepared human.

‘In the name of the Primarch and the Emperor Most High,’ began Cassius, ‘let the eve of battle be the prelude to our triumph.’

Cassius only needed to speak the first line of the prayer. It was one of hundreds every Ultramarine knew by heart, for they were collected in the Codex Astartes, and there was not a warrior present who had not memorised the sacred texts of the Primarch Guilliman. As the brethren kneeled in prayer, Cassius looked from one to the other – they wore their helmets even away from combat to counteract the planet’s toxic air, but he could still tell them apart by the squad markings and the nicks and dents in their armour.

Cassius was the oldest member of the Ultramarines aside from those who resided now in Dreadnoughts, and every member of these two companies had been recruited, trained and made into a Space Marine after Cassius had gone through that same process. Many of them he had chosen himself from the tribes and civilisations of Ultramar. He had found Captain Galenus of the Fifth in an interhouse war among the lesser aristocracies of Macragge, and spirited him away as a youth after he had slain four grown men in duels over his fallen house’s honour. Captain Fabian had been born to Talassarian sea tribesmen who fought an unending war against rival seaborne nomads and the monsters from the planet’s depths.

Cassius had shepherded them and dozens of others into the Chapter, and through battlefields without counting. To those battle-brothers he was the first Ultramarine they had ever seen in the flesh, and they still looked to him as an emblem of everything the Chapter represented.

As the prayer concluded, the strike force split up to attend to their wargear rites and private prayers. Cassius and the other officers of the strike force had set up a tactical holo-cartography chamber in one of the prefabricated hardened buildings. The buildings had been dropped from orbit along with the first of the Ultramarines’ vehicles. Captains Fabian and Galenus were already inside. The holomat was projecting a flickering map of the surrounding topography, unrolled in a broad swathe of grainy light. Blue icons hovered over the Ultramarines’ landing zone, marking the locations of the strike force’s units.

The hologram zoomed out, revealing the contours of the planet. Adverica was south of Kolovan’s equator, the smallest and least populated of the world’s three primary continents. Its rocky, tortured interior was ringed by dense rainforests to the sweltering north and a region of active volcanoes along the southern edge. The continent was divided by a deep fissure, and the expanse of land was sparsely dotted with settlements and industrial installations. Adverica’s three major cities were clustered along the northern shore, each with a population of several million. In that region the toxic air was counteracted by the atmospheric conversion towers along the coast, which filtered out the worst of the poisons to render the region habitable on a large scale.

It was very likely that every single Imperial soul in those northern cities was already dead. The tyranids had already swarmed across Estenia and Oriobis, the two larger western continents, overrunning whatever pitiful defences the now-deceased planetary government had managed to throw together. The population would have been hunted down and slaughtered. Then the feeder-beasts would have descended, consuming every scrap of biological matter on the surface, churning the corpses of a hundred million loyal servants of the God-Emperor into a gene-broth to be siphoned up by the xenos’ circling hive ships. Cassius had seen it happen to a hundred worlds, had read archives of data and analysis from the Imperium’s foremost experts on the tyranid menace. Every time he thought the fires of his hate for this foul species could burn no brighter, he found new fuel for his rage.

For now, they could only hope that the tyranids had not yet established their digestion pools and harvesting organisms on Adverica. If they had done so, and if they gathered enough biomass from the population, they could spread to infect dozens of nearby worlds, including planets of major strategic import such as Ryza. And then, too vast to stop, they could continue on world by world, on a pathway that would eventually lead them straight to Terra. This planet was already dying, but if they could hold the tyranid advance here, its death could at least serve to prevent other Imperial worlds from suffering the same fate.

‘Shipmaster Vanheuten has forwarded the geo-survey from orbit,’ said Captain Galenus as Cassius entered.

‘How are the men?’ asked Fabian. He was a veteran of the old breed, with his solid, grizzled face now revealed since he had removed his helmet. He had an open, agreeable look, and the men of the Third trusted him absolutely.

‘Their souls are sound,’ said Cassius. ‘The engagement with the xenos has roused their spirits.’

‘Name me an Ultramarine who doesn’t enjoy shedding tyranid blood,’ said Fabian. ‘I am more concerned with them losing focus and pursuing vengeance above victory.’

‘Then rein them in,’ said Cassius. ‘That is the burden of your command. The depth of our brothers’ hatred is from where they draw their greatest strength, and I shall bring those depths to light.’

‘We have to revise the next stages of the assault,’ said Captain Galenus, cutting to the quick as usual. Galenus was a straightforward soldier with little time for the weapons of symbol and sermon. ‘The tyranids hold more ground, and closer, than we anticipated. Their immediate objective on Adverica is the biomass of the northern coast. Once the xenos have a complete grip on this continent they’ll use aquatic bioforms to cross the ocean and take the rest of the planet.’

‘That’s what we’re here to prevent,’ said Fabian.

‘But they can put pressure on us here,’ continued Galenus. ‘This foothold isn’t a fortress. A major concentration of tyranids is gathering to the east past the fault, and they can mass against us with very little notice.’

Cassius fell silent, studying the geographical data intently, searching for something, anything, they could use.

‘This fault,’ he said, pointing at the gouge in the earth that separated Adverica from coast to coast in a great horizontal slash. ‘Is it stable? The geometry of this region suggests it has a history of volcanic upheaval.’

‘The geo-survey indicates that to be the case,’ said Fabian. ‘Energy readings suggest that Kolovan’s outer core is especially volatile. Earthquakes would be common in this region, close to the fault.’

Cassius nodded, and looked at Galenus and Fabian in turn.

‘As things stand, the tyranids can pour into this trench, cross it with ease and encircle us on the southern side,’ he said. ‘We must deny them this option.’

The two captains looked at each other.

‘You suggest we cause some sort of tectonic fracture?’ said Galenus.

‘I suggest exactly that,’ said Cassius. ‘We tear this continent in two and we drown the tyranids’ eastern swarm in the waters that pour in to fill the breach.’

There was a silence. Then Fabian laughed. ‘Fighting alongside you is always an enlightening experience, Chaplain. I will contact Shipmaster Vanheuten, tell him to start working on a bombardment plan.’

Cassius shook his head. ‘This will require greater precision than our vessels’ guns can provide,’ he said. ‘Do we have any heavy ordnance on board the Defence of Talassar? A siege device, or something similar?’

‘She carries a complement of cyclonic charges, I believe,’ said Fabian. ‘Used to undermine the structural foundation of major enemy fortresses, softening them up for artillery strikes.’

‘Contact the ship,’ said Cassius. ‘And send for Techmarine Lephaestus. Few are as learned in the art of siegecraft. He will know where to strike.’

‘This will buy us time,’ said Galenus. ‘But we still need to break the back of the main tyranid swarm in the west.’

‘So I see.’ Cassius followed the icons on the holomap. The enemy stained the north-western region of Adverica like a cancer. ‘If we are not swift, they will become too strong for us to crush.’

The tyranids on Kolovan were in the early stages of invasion, with basic combat organisms commanded by warrior-forms, but as time went on the more specialised organisms would be dropped from the hive ships or birthed from the nutrient pools. The tyranids would adapt to the strike force’s arrival and evolve new forms and weapons to fight their enemies – denser muscle fibre to drive claws through ceramite armour, heavier exoskeletal layers to turn aside bolter fire, swifter scout forms to detect their movements, and siege-beasts to overturn their tanks. The pattern had been repeated across thousands of worlds caught in the path of the tyranid hive fleets. It would happen on Kolovan too, if the Ultramarines did not shatter the tyranid force now.

‘So we must split our force,’ continued Cassius. ‘One half to the fault line with the charges, one half west to hold their advance.’

‘It is the only path available to us,’ said Galenus.

‘Then our purpose will see us through,’ said Cassius.

‘I shall take the Third westwards,’ said Fabian. ‘I know my battle-brothers would be glad to see Chaplain Cassius marching with them.’

‘I would not deny them the chance to tear out this infestation at its root,’ said Cassius.

‘And what kind of captain would I be,’ said Fabian with a smile, ‘if I denied them the sight of Lord Cassius smiting the foe?’

Cassius did not respond to that, and activated the controls at the base of the holo-projector. The map zoomed in to the region west of the Ultramarines’ foothold. The topography was as tortured here as the rest of the continent. Jagged valleys had been carved out of the desert, the largest of which formed a wide channel through which the massed horde of the tyranids could pour through into the heart of Adverica. From the centre of the image, facing the southern entrance of this great valley, rose a craggy mass of rock, solid where the rest of the region was shifting and broken.

‘Here,’ said Cassius. ‘A defensible structure. This canyon is the logical path through to the heartland. The xenos will pass through it. If we seize this position we can bottleneck the swarm, and thin their numbers before they reach us.’

‘It’s pre-Imperial,’ said Fabian. ‘Some kind of ancient fort built into the rock. Looks rugged enough. Acceptable lines of fire.’

‘That will be our objective,’ said Cassius.

‘Agreed,’ said Fabian. ‘By dawn we will have enough Rhinos dropped to transport both companies to their assigned mission zones. Still time to pray, Lord Chaplain.’

‘Then I will lead, for those who desire it,’ said Cassius. ‘Come the dawn we will strike out. And brothers, our souls will be prepared.’

The rising of the sun saw twin columns of Rhinos leaving the Ultramarines’ foothold and the protection of its automated guns.

Even with the main complements of the Third and Fifth Companies gone, the drop zone bustled with activity. By now a crew of labour-servitors had been dropped in landers to shore up the defences, along with a squadron of gun-servitors to further deter tyranid incursions. Sergeant Verigar, who had lost two fingers of his right hand in the cleansing of the landing zone, remained at the base camp with a small detail of Ultramarines, and it was one of his squad that spotted a new fleck of darkness in the sky above.

‘Has it opened communication with us?’ Verigar asked Brother Morvion, who was operating the vox.

‘Aye, sir,’ Morvion replied. ‘It’s a Mechanicus vessel, the Castraneta, requesting landing.’

‘Finally they show,’ muttered Verigar. ‘One ship should turn back the tyranids, I’m sure. Give them authorisation to land. Let’s see what they want.’

‘It’s bleeding fuel and spewing smoke,’ said Morvion. ‘They’ve taken a bad hit.’

As the ship descended the gun-servitors turned their heavy stubbers skywards and Verigar ordered the sentry guns recalibrated to face the unexpected arrival. No sense in taking unnecessary risks. As the ship descended it coalesced into the shape of a small, swift cutter in burnt orange livery, belching smoke from a crater torn in its rear engine.

The cutter landed inside the Ultramarines’ foothold, and Verigar ordered the servitors to hold fire. Up close, some sort of elaborate iconography that Verigar could not place was visible on the side door of the cutter that now opened to allow a figure in deep orange robes to disembark.

Sergeant Verigar waited as the new arrival stepped out onto the dry earth. An honour guard of once-burnished valet servitors descended after him, now stained black by the thick smoke.

‘Greetings, Space Marine,’ said the newcomer in a voice that sounded like the grinding of steel blades.

The leader was roughly humanoid, though like most members of the Mechanicus he had been extensively augmented. One of his arms was fully mechanical with a complex claw incorporating several different tools, while the other was human but with flesh the blue-grey of a corpse. His head was hidden in a deep hood into which led several wires and cables, attached to the brass-cased rebreather unit mounted on his hunched back. His robes were patterned with bands of crimson and embroidered with mottos in the obscure alphabet of Lingua Technis. The human hand held a staff of office carved from ivory and topped with a brass cog.

‘I am Magos Xenopathologis Uranios Rothe,’ the figure continued, ‘representing the archmagi of Blessed Ryza.’

‘Greetings, magos,’ said Verigar. ‘Sergeant Verigar of the Ultramarines Third Company. I would ask you to explain your presence here.’

One of the scorched valet-servitors shuffled forwards and unfurled a pennant covered in intricate heraldry, comprising several hundred lines of binary code surrounded by laurels and cogwork.

‘I am a representative from Adeptus Mechanicus research complex Zeta-Epsilon Twelve,’ Rothe said, ‘located one point zero three miles underneath the northern city of Harienza. Approximately seventy-four hours ago the tyranid swarm consumed the last vestiges of the city’s militia regiment, and we were forced to enact emergency lockdown procedure Alpha-Three. We request your assistance in evacuating personnel and equipment of great importance.’

The magos looked at the blazing ruin of his cutter. The promethium tanks that fed the engine had ruptured, and flames now wrapped the entire vessel. The metal of the cockpit hissed and groaned, and collapsed in on itself, sending another tongue of flame shooting into the air.

‘It is unlikely that my own transport vessel will suffice,’ Rothe said.

‘My commanders are taking the fight to the tyranids,’ said Verigar. ‘They will be informed of your arrival. But this is no rescue mission, magos. The Ultramarines are here to contain the xenos threat, not extract survivors and lab gear.’

The magos released a lengthy splutter of binaric that Verigar did not understand. He guessed that it was not entirely complimentary, and his eyes narrowed.

‘Sergeant,’ Rothe rasped, ‘the research that is being carried out at Zeta-Epsilon Twelve is of the utmost importance. I must demand your immediate assistance in securing it.’

Verigar looked the tech-priest up and down.

‘I’ll explain this very clearly, magos,’ he said, emphasising every word. ‘This is an Ultramarines operation. You do not make demands here. Unless you have a spectacularly good reason for us to retrieve it, your precious data can rust and rot as far as I’m concerned.’

The magos released another indignant blast of binaric, accompanied by a faint whirring sound as he clenched and unclenched his bionic claw.

‘I have no time for your obstructive attitude, sergeant,’ said Rothe. ‘For the last twenty-nine years, seven months and eighty-six hours, I have been working on a theoretical model for the large-scale application of bacterial pathogens designed to flood a xenoform host with lipoglycan endotoxi–’

Verigar held up a gauntlet.

‘What do you mean? Biological weapons?’ he asked.

‘That is a most reductive interpretation,’ replied Rothe. ‘The implications go far beyond simple biological warfare. My research could lead to a new understanding of the physiological susceptibility of the xenoform to biosynthetic microbes.’

Verigar nodded thoughtfully.

‘It will still have to wait,’ he said.

Rothe spluttered so much that the sergeant genuinely thought a vital gear had come loose somewhere inside his mechanical form.

‘Magos,’ Verigar said, patiently, ‘recovering your research data will make no difference if the tyranids break through into the mainland and overrun our position before we can utilise it. As we speak, the Third and Fifth Companies are rushing to slow their advance. I will contact Captain Fabian and inform him of this information. When he and the Third Company return, we will discuss your findings.’

Verigar glanced from the cutter to the distant plume of smoke and dust vanishing eastwards, in the wake of the Third Company’s advance. Maybe the Adeptus Mechanicus had a weapon that could deliver Kolovan. Perhaps the Ultramarines would shatter the xenos hold on the world and the weapon would not be needed. Whatever the outcome, a great many tyranids would have to die first.

At the edge of the Transadverican Canyon, looking out to the rocky wastes on the eastern side, it was possible to appreciate how complete the tyranid infestation had become. The far side teemed with tyranid battle-organisms, from the masses of scuttling termagants and ripper drones to lumbering siege-forms that served the hive mind like tanks served the armies of the Imperium. Clouds of steaming spores, the cast-offs from the tyranids’ rapid evolution, rose into the air and cast an uncharacteristic shadow across the desert.

Captain Galenus leaned from the upper hatch of his Rhino and held out a hand. Discoloured water pattered against the palm of his gauntlet.

‘I wonder how many years it has been since this desert last saw rain,’ he said.

‘The tyranids twist everything they touch,’ said Sergeant Kytheos, who led Galenus’ command squad.

‘They hurl spores and bio-organisms into the skies,’ said Galenus. ‘They torture the earth and reshape it to suit their own foul needs. This planet is dying, and these are the symptoms.’

‘They will burn for this,’ said Kytheos. ‘All of them.’

The canyon itself was six thousand metres deep, formed by a join between the two main tectonic plates that made up the Adverican continent and carved deep by long-dried rivers. Dozens of exposed strata spoke of the planet’s troubled geological history. From the eastern desert the tyranids were spreading north into the equatorial plains, and westwards to link up with the concentration that was heading towards Cassius’ objective.

The eastern desert would have to be cleansed. If Cassius and Fabian could hold back the advance of the main assault, the strike force could reconvene and mop up the eastern infestation while it was occupied trying to force itself a way to the coast. It would be driven into the sea and Kolovan would be delivered. But first, the Ultramarines had to split the tyranids and ensure they were not surrounded.

‘The Defence of Talassar reports that the Stormraven is on its way,’ said Kytheos. ‘The charge will be down in less than four minutes. Vigilant Beta has a visual.’

‘All units!’ voxed Galenus. ‘Move to Vigilant Beta’s position! Make ready to engage!’

The Fifth Company’s ten Rhinos gunned their engines and rode up over the ridges of the broken desert, wheeling northwards and driving parallel with the edge of the Transadverican Canyon. The xenos host stirred as the roar of engines echoed between the stratified canyon walls. Winged tyranid scout-forms flittered out over the far side of the canyon, already swooping towards the armoured column like carrion birds expecting a meal.

The Stormraven Ausgustia, launched by the Defence of Talassar and flown by Brother Axil, the company’s finest combat pilot, roared overhead of the column, and came to rest several dozen metres from the lip of the chasm. The Rhinos circled the landing site, top hatches opening for the Ultramarines inside to mount storm bolters and scan the sky for potential threats. Others disembarked from bulky access doors that clattered open on the vehicles’ sides, weapons readied. Galenus was the first out, running over to the Stormraven, accompanied by his command squad and Techmarine Lephaestus.

Usually designated as transport vessels for squads of Space Marines, this particular Stormraven had been customised to transport an even deadlier payload. The bullet-shaped cyclonic charge was nestled in the craft’s rear grapples, which had been reinforced and buttressed by criss-crossing plasteel girders in order to provide a secure carriage for the ship’s volatile cargo. The charge itself was almost as tall as a Space Marine, and measured a good couple of metres in width. Its rough steel casing was etched with holy scripture. The red-armoured Lephaestus used the servo-arm attached to his armour’s backpack to pry open a panel on the side of the device, beneath which was a series of arcane data readings.

‘Is it intact?’ Galenus asked. His command squad were already forming a defensive line and the rest of the strike force were creating an impromptu defensive position anchored by their Rhinos.

‘There is no breach,’ replied the Techmarine. ‘Let the Omnissiah be praised. The machine-spirit is fit for libation.’

‘Be quick about it,’ said Galenus, who had little time for the ceremonies taught to the Techmarines by the priests of Mars.

Tyranid war-forms were already scuttling across the canyon floor towards their position. The Ultramarines formed up in firing lines on the ridge, directed by their sergeants to create overlapping fields of fire in the direction the tyranids would approach from. Galenus watched the precepts of the Codex Astartes being ticked off in his mind, the angles and mathematics of combat falling across the battlefield in a mental map, the endless streams of battle-lore spooling through his memory. Mutually supportive firing zones. The reserve ready to swing up and create a crossfire. The assault units preparing to charge through the tactical units and counter-charge the tyranids. Guilliman himself could not have drawn the battle lines more sharply.

Techmarine Lephaestus scattered sacred machine oil from an aspergillum onto the cylinder. It spat and hissed where it touched the still-hot casing. Lephaestus murmured in High Gothic as his servo-arm held up a data-slate with numbers streaming across its glowing screen. He turned to the captain.

‘We will need to take the device down into the canyon,’ he said.

Galenus cursed. Of course.

‘It needs to be primed and placed at exactly the right point,’ Lephaestus continued. ‘We must create a nucleation zone of catastrophic size at a point where the mantle of the planet is weak enough for the detonation to bring about a seismic event.’ He held up the data-slate. ‘Readings suggest that there is such a point one thousand, two hundred and thirty-five metres across the canyon floor, a shallow depression where the crust of the planet is brittle and thin.’

Twelve hundred metres. That would buy them some time, thought Galenus. The canyon was five kilometres across at its narrowest point, which meant that the tyranid swarm would take several minutes to reach them.

‘Captain!’ came a vox from Vigilant Gamma. ‘We have airborne organisms coming across the canyon towards our position.’

Galenus turned to see the shadow lifting up from the far side of the canyon. It consisted of scores of winged scout-forms, dubbed gargoyles, surrounding a larger winged creature that trailed a nest of barbed tendrils from its underside. It was the size of a fighter craft, and the gargoyles whirled around it as if it was on a bombing run and they were its escorts. Time was running out.

‘Assault Squads, to me,’ Galenus roared, signalling Brother Axil in the Stormraven to fire up his engines. ‘Brother Axil, you will take me and my command down into that canyon. We will hold off the tyranids long enough for Techmarine Lephaestus to place the charge.’

The captain turned to the Assault Marines, who were led by the veteran Sergeant Rullus, a big man even by Adeptus Astartes standards, with a shaven head and a vicious burn mark across the left side of his face. He wielded an eviscerator chainsword in two hands, holding the heavy, cumbersome weapon as easily as if it were a child’s toy.

‘Follow us in, sergeant,’ Galenus said, ‘and form up around the Stormraven. Buy us time.’

Rullus nodded grimly. He knew the risks here. Without the support of the rest of the company, they would be horribly exposed on the open ground of the canyon floor.

‘Sergeant Vorrux, lead the rest of the company away from the detonation area. You cannot help us here, and we must maintain a second front in case something goes wrong. Get well clear, but keep the engines running – we may need you.’

Dust was thrown up in great plumes as Brother Axil gunned the flyer’s engines. The Stormraven’s access ramp lowered, and Galenus and his squad thundered into the transport hold. The captain felt his stomach jolt as the gunship lurched into the air, and grabbed a restraint harness to steady himself. As they passed the lip of the chasm, Axil threw the Stormraven into a steep dive, abandoning a smooth, safe flight in favour of expediency.

In the Stormraven’s wake, Sergeant Rullus and his Assault Marines charged to the cliff edge and hurled themselves into space, firing their jump packs as they went. The burn of their thrusters sent the Space Marines soaring in a wide arc towards the canyon floor thousands of metres below, which rushed up to meet them eagerly. With judgement honed from thousands of airborne assaults like this, each Ultramarine tempered his terminal velocity with periodic bursts from his jump pack. Their timing was so precise that each came down to earth in a sprint, hurtling towards the Stormraven that was circling the landing zone ahead.

‘Guns live!’ shouted Axil over the vox, swinging the gunship around to face the aerial assault, which was bearing down directly towards them. The lead tyranid flyer’s face split open, revealing a cannon barrel grown from its oversized tongue. Its forelimbs were adapted into scything blades that could slice a tank in two.

There was a chattering roar as the Stormraven opened up with its forward-facing assault cannons. Clouds of bloody smoke erupted along the tyranid line as mass-reactive rounds found their targets and detonated, sending shards of metal and shredded chitin ripping through the airborne swarm. Axil’s gunner loosed a missile which left an arcing contrail as it zoomed towards the lead flyer. The massive creature dipped its wings at the last possible second, and the missile flew past and impacted in the gut of a bloated horror with two obscene weapon-growths protruding from its torso. A gout of flame and the resulting supersonic shock wave tore the creature to bloody chunks and rippled through the smaller creatures trailing in its wake, sending dozens toppling from the sky.

In a daunting display of piloting skill which Captain Galenus swore he would cite for commendation if any of them made it out of this alive, Brother Axil cut the Stormraven’s forward motion and raised the nose of the craft, descending the remaining dozen metres or so to the target zone while still maintaining a full cannonade at the onrushing tyranids. As he reached the torn, jagged canyon floor, Axil lowered the forward ramp, and Galenus and his men poured out.

Ahead they could see the tyranid infantry hurtling towards them, only a few hundred metres away now. Protrusions of igneous rock provided some cover, but the canyon floor ahead of them was largely open. Behind them, to the rear of the gunship, the ground sloped down slightly to form a crater several metres across. This was the spot Lephaestus had recommended. The Techmarine was already using his servo-arms to detach the grapples that secured the cyclonic charge. Galenus and Brother Hetrus ran to his side, and together the three began to drag the device to the centre of the crater.

Brother Axil cursed over the vox, and Galenus looked up to see a shadow fall across them. The monstrous flyer descended, jaws stretching wide to reveal a colossal weapon-organ that dripped with foul bio-acids. The monster’s skin was pockmarked and blistered by bolter fire, but still it came on, seemingly unconcerned by its ruptured flesh. Living missiles detached themselves from the creature’s wings and hurled themselves at the Stormraven. Metal screamed and shattered as they impacted, and arcs of electricity wracked the cockpit. The tyranid spat a stream of acid from its mouth-cannon, and the vitriolic spray hissed as it splashed across the gunship’s viewport, washed over the top of the vessel and splashed across the Space Marines dragging the charge into place. Galenus growled in fury as he felt the acid sear into his gorget. Warning runes flashed up on his visor’s tactical display, and he blinked them away in irritation. The shadow passed over them as the tyranid flyer swept around in a great arc, lining itself up for another attack run.

Brother Hetrus was down. Galenus went to roll him over, and saw the smoking, melted ruin that used to be his face. The acid stream had hit him directly. Lephaestus was also sprawled on the ground, though Galenus could see him dragging himself to his feet, plasma pistol raised in one hand.

‘The device!’ Galenus shouted. The air was filled with the smell of scorched metal and seared flesh. Lephaestus staggered and fell against the cyclonic charge. His armour was smoking, the cog icon on his breastplate that marked him as a servant of Mars had melted away, and Galenus could see raw, red flesh beneath. The Techmarine pulled at the panel on the side of the device. It curled and came apart in his hands.

‘The activation panel is gone,’ Lephaestus gasped, his voice taut with agony. ‘Melted away. I intended to set the timer myself, once we had it in place.’

Galenus grabbed him by the shoulder. ‘Can we still detonate it, brother?’

The Techmarine looked at him and nodded slowly.

‘I can,’ Lephaestus said. ‘Manually.’

Galenus growled in frustration, and struck the canister with a gauntleted fist.

‘Please, captain,’ said the Techmarine, ‘Do not manhandle the device. Its spirit is angry enough already.’

Galenus could not help but smile. He clapped Lephaestus on the shoulder.

‘We will buy you the time, brother,’ he said.

‘It’s coming back around,’ Sergeant Kytheos shouted, bounding down the slope towards them. He had his custom bolter in hand and Galenus drew his power sword. It had a short, broad blade in the tradition of Macragge, with the symbol of his Chapter in lacquered blue on the hilt.

‘Brothers!’ he shouted. ‘We cannot yield this ground!’

Behind whatever cover they could find at the top of the slope, the Ultramarines let loose a barrage as the gargoyles passed into firing range. Dozens fell as the precision taught on the firing ranges of Macragge picked them out from the sky. The gargoyles returned fire from the fleshborers formed from their limbs and Galenus unhitched the storm shield hung on his back to fend off the hail of ravenous organisms. They splatted and thunked into the shield, and he glanced with disgust at the way they wriggled feverishly in the dirt where they landed around his feet. The enemy flyers dropped lower, and the barrage ceased as they picked up speed, skimming towards them across the ground. Closer they came, closer and closer…

‘They close to blade range,’ shouted Kytheos. ‘Scores of them.’

Galenus shook his head. They were only eight men. Where were the Assault Marines?

His question was answered by the throaty roar of a firing jump pack. Sergeant Rullus and his force met the tyranid flight in mid-air, hurtling over the heads of Galenus and his men to crash into the gargoyles with the bone-cracking force of their momentum. Rullus swept his eviscerator in a wide arc, and simply let the oncoming organisms dismember themselves on its teeth. More Space Marines hurled themselves into the fray. Swathes of flame enveloped enemy creatures, sending them crashing to the ground in heaps of screaming, burning flesh. The crack of bolt pistols and the grinding tear of impacting chainswords was a blessed symphony to Captain Galenus’ ears.

The captain drew back his shield and thrust his blade up to meet a gargoyle bearing down on him. The blade sheared through its forelimb and the creature was on him in a flapping of wings and snapping of teeth. Galenus got his shield under it and flipped it off him to the ground, despatching it with a sword-thrust to the throat. The power field burst to rip its head clean off and leave its upper torso a mass of torn and oozing organs.

The stench was awful. It was not just foul, like the rancid effluvia of a city, though that was bad enough. It was inhuman, a cocktail of chemicals that had not formed by any natural process in this galaxy, for the tyranids – the Inquisition hypothesised – were from another region of space entirely, and had drifted to this one after aeons dormant in the void. If there was ever proof of the utter disconnect between the tyranids and any living thing in the Emperor’s galaxy, it was the stink that billowed out of that torn organism, scorched by the swords’ power field and free to flood out across the desert rocks.

As his brothers tore into the smaller creatures, Galenus hacked around him to open up enough of a space to take stock of the situation. The shadow of the huge flying creature swooped closer, lower than before, aiming not for the stricken Stormraven, but for Galenus himself. The captain leapt up onto a nearby spur of rock to give him an extra metre or so of reach.

The bio-cannon extended from the huge flyer’s jaws. Its tiny yellow eyes were focused on Galenus. The captain stood his ground, daring the creature to open fire at him, daring it to rake down at him with claws and tendrils.

The bio-cannon belched another mass of fizzing acid. This time Galenus threw his shield up in front of him taking the weight of the blast against it, planting his back foot to keep himself upright under the torrent. He could feel the hiss of decaying ceramite as acid ate through the front of the shield and stray gobs of it bubbled against his armour.

The flyer let out a rising shriek as it closed. Galenus threw the ruined shield aside and raised his sword. The flyer’s tendrils unspooled beneath it in a forest of writhing flesh, and twin blades sliced towards him. He swung his sword overhead and felt the impact as it smashed through the first blade in the flash of the discharging power field. The captain leapt to one side as the second blade whistled over his head and the tip of his sword punched up into the thick, fibrous tissue of its wing root.

The sword carved through the base of the flyer’s wing. Tendrils whipped and twined around Galenus’ limbs as the sword bit deeper and finally came free, the half-ruined wing left useless.

The flyer, unable to gain height again, dragged Galenus with it as it slammed into the ground. Galenus rolled with the impact, kicking free of the tendrils and forcing the weight of the creature off him. The rest of the command squad leapt onto the beast, with Kytheos pumping half a magazine of bolter fire into the side of its head. The flyer died butchered on the ground by the bolters and blades of the Ultramarines.

They would hold, but not for long. Galenus could not order them to defend this position indefinitely. The leading edge of the tyranids’ ground swarm had already reached the forward line of the Assault Marines, and Galenus could see brothers going down under the mass, chainswords still swinging defiantly.

Time. It was always about time. There was never enough.

‘Lephaestus!’ shouted Galenus. ‘What is the status?’

‘The machine-spirit approves of activation,’ said the Techmarine. ‘This will work.’

Galenus was about to order Lephaestus to blow the thing, when he heard a crackle over the vox.

‘Captain,’ said Brother Axil. He sounded like hell, his words thick and wet as if he was choking them out through a mouthful of blood. Possibly he was. ‘Ausgustia still lives. She’s taken a hell of a beating, but she can make it out.’

Hope. The Emperor saw fit to dispense it at the most unlikely moments.

‘Fire the engines, brother,’ Galenus shouted. ‘Sergeant Rullus, do you hear me? Retreat, back to the gunship.’

The captain sheathed his sword and ran through the mass of torn flesh and entrails which was all that remained of the huge tyranid flyer. A few of the gargoyles still lived and fought on by instinct, flapping and screeching as bolter fire stuttered up to shoot them down, but the aerial assault had been blunted. Ahead, the screen of Assault Marines held the ground swarm at bay, but they were too few to occupy the tyranids for long.

‘Captain,’ Rullus shouted over the vox. ‘Get clear. We cannot pull back, we’re surrounded. We’ll make them pay, Captain, for ev–’

Rullus’ voice was drowned out by the crack, crack, crack of a bolt pistol discharging, and a hissing, alien shriek so high-pitched that it reverberated around Galenus’ skull, shaking his teeth. There was nothing to be done. The swarm enveloped the Assault Marines, who stood tall and proud, true Ultramarines to the end, as a torrent of flesh washed over them. Galenus could see flashes of glorious blue amidst the hideous pale, swirling mass of warrior-organisms. His soul ached, and he wanted nothing more than to charge into the fray to aid his brothers, but he could not leave the Fifth Company leaderless.

‘To me!’ he shouted, and his command squad filtered back into the hold of the Stormraven. Brother Phiron had lost a leg, and was being carried by two of his fellow warriors, still roaring oaths of vengeance as he went. Four more of Galenus’ most trusted warriors would never leave this canyon. There was not even time to secure their gene-seed.

As the last of the Ultramarines staggered aboard, Brother Axil kicked the gunship’s thrusters and it rose into the air, screeching in protest and raining fragments of twisted and warped metal onto the canyon floor. As the ramp closed and the Stormraven swung back towards the southern wall of the canyon, rising slowly, Galenus caught one last glance of Techmarine Lephaestus, slumped next to the cyclonic charge, gun in hand, one servo-arm tearing at the metal canister. Lephaestus raised one arm to his chest in salute. Then the ramp rose to cut out the harsh yellow sun of Kolovan, and he was gone.

‘Mars will hear of your sacrifice, brother,’ the captain whispered.

Techmarine Lephaestus watched as the tyranid horde rushed towards him. Did they know, he wondered? Was the wretched alien consciousness that gave them motion aware that its doom was at hand?

By the Omnissiah, his chest hurt. He was a veteran of a hundred campaigns on a thousand planets, but he had never felt such pain. He could still hear the hiss of the bio-acid as it ate at his flesh, devouring his insides with hateful efficiency. Breathing sent a torrent of agony flooding through his body. A lung had collapsed, then. That was probably one of his less catastrophic injuries.

It did not matter.

The captain, Emperor protect him, was clear, and the Fifth had hopefully retreated far enough that they would escape the coming cataclysm.

His servo-arm tore away the plating at the side of the canister, exposing wiring and circuitry, the beating heart of the cyclonic charge. This was not the right and proper way to send such a blessed device about its holy purpose, but Lephaestus hoped its vengeful machine-spirit would understand.

As a shrieking tide of foul creatures swept down the slope of the crater towards his ruined form, Techmarine Lephaestus placed the barrel of his plasma pistol against the exposed interior of the charge, and fired.

The canister delivered from the Defence of Talassar was a fortress-killer, a bluntly efficient warhead capable of ending potentially brutal sieges before they had even begun. Each cyclonic charge contained a cluster of gravitational explosives that created a chain reaction, seeking out the densest material and ripping it apart until the reaction died out far within a planet’s crust. Even the most solid foundations would be torn asunder, and the resulting tectonic upheaval would collapse fortified enemy positions with contemptuous ease. In sufficient numbers, they could rip a planet apart. A single charge could not destroy a world but, when deployed at the right location, it could rearrange the surface of one.

It detonated at a critical spot in the base of the Transadverican Canyon. The first rippling band of explosions tore a hole into the earth, driving the inner bundle of gravitational munitions into the ground. A plume of dust and pulverised tyranid corpses was thrown into the air, rising high above ground level.

The ground shuddered. Fissures opened up in the broken earth and chunks of rock toppled into the yawning depths. The canyon wall on the far side of the chasm sloughed off in great chunks, spilling dozens of bio-forms into the abyss. They kicked and squirmed uselessly as they fell. With a terrible sound like the planet itself groaning in pain, the gravitic charges went off and a shock wave of rapidly changing density radiated outwards deep into Kolovan’s planetary crust. Strata of the densest rock liquefied. Thousands of cubic kilometres of sedimentary stone were turned to dust.

The far side of the canyon dropped thousands of metres in just a few seconds. The tyranids gathering there vanished in a mass of pulverised rock that rose in an enormous black cloud. The canyon itself was torn open like an old wound, rippling heat distorting the dust clouds billowing above it as molten rock rushed up from below. A huge sheet of lava was hurled into the air as the canyon was forced open still wider.

The rumbling decreased in volume and pitch as it reached the lowest depths of the planet’s crust. The lava’s pressure was spent and the shuddering halted. The detonation and accompanying earthquake had widened the canyon by half a kilometre and transformed the surrounding area, further breaking up the rocky desert, collapsing ancient underground caverns and riverways and opening up new voids beneath the earth.

It went quiet, for a time. The initial shockwaves and eruptions faded to a low rumble.

But it was not over.

The rushing sound came from the north. It was quiet at first, mingling with the rattling grind of the Stormraven’s engine, but Galenus’ enhanced hearing picked it out as it rose. A white plume breached the horizon as the waters approached.

The Transadverican Canyon did not reach quite to the coast. There, the tectonic plates overlapped to form the highlands of the rolling equatorial rainforests. But the cyclonic charge changed this, tearing the canyon open to the coast and beyond, breaching the limits of the northern ocean. The waters were first flashed to steam by the burst of lava from below, and then rushed in to fill the new, dry river that had opened up, reaching right through the centre of the continent.

The waters poured in from the south, too, where the polar ocean inundated the networks of caves and underground lakes suddenly opened up by the plate margin’s opening. But it was from the north that the torrent came fastest. It roared past the site of the battle, carrying thousands of organisms living and dead to be battered to pieces against the jagged rocks. The flow rushed back and forth, ripping tonnes of rock off the canyon sides and further opening up the new bleeding wound across the continent.

‘Relay to Cassius’ force,’ said Galenus into the vox over the sound of the rushing waters, loud even here as they soared out over the open desert. ‘The cyclonic charge detonated successfully. Objective accomplished.’

Chapter Three

The first thing the Ultramarines heard was a low rumble, which rolled across the earth towards them until it became a deafening roar. The earth shook beneath their feet, cracks widened and splayed, and the vox screamed with static. From the east they saw the clouds, mighty swathes of displaced ash that had been hurled into the sky by a seismic event of horrific, planet-altering power.

Cassius kneeled and placed his palm against the ground. Through his gauntlet he could feel the shuddering of the earth, and the distant moaning of Kolovan’s pain reached his ears.

‘Galenus has been successful,’ he said.

‘Did you ever doubt it, Chaplain?’ asked Captain Fabian. They stood on the ramparts of the fortress the Ultramarines had designated Sigma Fortulis, staring down at the pass that it guarded. ‘The Fifth have done their job and we’ll do ours.’

Sigma Fortulis was a massive outcrop of wind-sculpted rock, overlooking a pass through two regions of broken and impassable uplands. On either side of the level ground, shattered spurs of rock reached up to the sky, inhabited only by the lizard-like raptors that wheeled around their uppermost peaks. The fortress itself was of stratified rock, the softer layers worn away by the action of the stinging desert winds, and as a result several low, cramped galleries were hollowed out in the rock’s interior.

Some forgotten pre-Imperial tribe had turned the natural structure into a strongpoint against enemy nomads. They had burrowed tunnels into the rock to access the upper levels, fortified some areas and enlarged others, and created a primitive but solid structure that the spears and arrows of their foes could not breach. Whole generations had presumably inhabited the cell-like living quarters cut into the heart of the rock, and defended it with loose rocks hurled from the upper levels or the simple capacity to wait out any siege.

Now, it was a bulwark on hostile ground, a defensible point upon which the Ultramarines would thin the numbers of the tyranid swarm. Fabian had placed his Devastator squads along the wall, heavy bolters to the fore. The remaining hundred men of the company were arranged in their Tactical squads, scattered throughout the structure. The muzzles of their guns were pointed towards the mouth of the canyon, beyond which the enemy gathered. They could see flyer organisms circling in the darkening air, and through the heat haze of the canyon a host was on the move. Xenos spores drifted overhead like seedlings from a great tree. Thicker and thicker they came, in clouds so dense they began to dull even Kolovan’s angry sun. A shrieking, hissing crescendo came from the pass. It would begin soon, Cassius knew.

Sergeant Remas and his men approached. Fellow Ultramarines nodded in respect as they passed; any warrior who had made it through the hell of the Tyrannic Wars was elevated in his brothers’ eyes.

‘Auspex scans indicate that the first few floors of the structure are clear,’ Remas said. ‘There’s no time to make a full search of the lower chambers, but they seem to consist of burial tombs and mausoleums. This fortress runs deep into the earth.’

‘It does not seem to warrant the name of a fortress,’ said Brother Edrius, of Fabian’s command squad. He held the company banner in one sturdy hand, flying it high over the wall so that every warrior nearby could draw inspiration from its storied history.

‘The people of this world once made it so,’ replied Cassius. ‘We shall do so again.’

‘They will soon be upon us,’ said Remas. ‘They will see this place and they will pour into it like water.’

‘We will break them here, brother,’ replied Cassius. ‘This position is a defensive bulwark straight from the pages of the Codex. Strong walls, clear lines of fire. The Emperor has graced us with the means to obliterate these wretched creatures.’

‘I’ve heard the same thing said before,’ said Remas quietly.

Remas wore the mark of the Tyrannic War veterans, but he was no Ultramarine. His own Chapter, the Scythes of the Emperor, had been devoured by the maw of Hive Fleet Kraken. As far as Cassius knew, Remas was the sole survivor. Reports had filtered through of other bands of Space Marines wearing the Chapter’s black and yellow colours launching themselves on suicide missions against high-value tyranid targets, but as yet they went unconfirmed. The Chaplain did not usually have time to waste on pity, but he could hardly imagine how it felt to carry the weight of all those dead brothers. He hoped the carnage that Remas had wrought on the xenos in the years since had provided some comfort.

Captain Fabian hurried in Cassius’ direction. ‘The Defence of Talassar is relaying a bio-reading spike through the pass,’ he said. ‘I’ve had the Rhinos lined up outside the walls, blocking any entrances and weak points.’

‘We will lose them,’ replied Cassius.

‘We will,’ said Fabian. ‘I will not drive them into the teeth of a tyranid advance when we have a defensive position, but equally I cannot send them away. Their guns will be needed.’

‘So be it,’ said Cassius.

The Chaplain and the veterans descended into the fortress. Its stairways and passages were for normal-sized humans, and the Ultramarines had to stoop and squeeze their way through to the wider galleries. Primitive carvings of Kolovan’s ancient gods covered the walls – a plump fertility goddess, a spindly red-skinned daemon, an axe-wielding kingly god who looked down from the clouds. The Third Company’s heavy weapons units were stashing ammunition at key junctions, acting on the Codex’s precepts for maintaining mobility through a defended structure.

Cassius reached one of the lower hollowed-out strata that stood open to the desert. The walls were scalloped and rippled from the action of the wind carving into smooth hollows.

‘Deploy here,’ he said to Remas. ‘Keep the watch and notify me if you see anything unusual.’

He walked up to the edge, where the rock gave way to a sheer drop. With the overhang and the smoothness of the rock he could appreciate how difficult it must have been for a primitive human enemy to assault this place, though he wondered if the tyranids would find the climb such a hindrance. They would soon find out.

‘They’re on the move,’ said Remas, racking the slide of his bolt pistol.

The enemy seeped out of the valley in a roiling tide of pale flesh that surged towards the Ultramarines’ position. Above them came the flyers, bat-winged and hideous, bearing gun-organs and acid-spewing mouths. On the ground and in the sky there were so many of the creatures, packed so closely together, that Cassius had trouble picking out individual xenoforms, but this first wave seemed to consist of the smaller, faster organisms. That was consistent with typical tyranid assault behaviour. These wretched things would die in their thousands, but every death would cost another bolter round, every hundred deaths another Ultramarine life. It was the simple, ruthless economy of war that won most battles in the tyranids’ favour.

Not here, thought Cassius. They had come prepared. Ammunition pods were scattered throughout the complex, within easy reach of each fire team; there was an unthinkable amount of firepower ready to be hurled into the xenos ranks. Dozens of anti-personnel mines had been placed in the killing field, adjusted for remote detonation so as to ensure the maximum number of casualties.

The bolters opened up, ripping into the front ranks of the alien advance. Bursts of grey and pink smoke marked scores, then hundreds, of deaths. Bodies collapsed, swept up under the momentum of the rush, ground to pieces. Flyers spiralled from the sky, swallowed up in the torrent of biological matter. As the swarm reached the foot of the wall, the mines went off in a series of concussive detonations that shook the fortress. Dust and loose stone fell from the ceiling above the veterans’ position.

‘It was like this on Sotha,’ said Remas, watching from the ledge beside Cassius. ‘When they came to assault the fortress-monastery. I watched them send waves of creatures into our guns. We even dared to hope that this was the way the battle would go and the idiot xenos would walk to their deaths. But they were just measuring the strength of our defences so they could go around them. When the real assault came, we just couldn’t fire fast enough. They hit us at every weak point. It took them weeks, but we fell.’

‘Captain Galenus has completed his mission, sergeant,’ said Cassius. ‘They cannot bring their full weight against us here.’

‘They have no shortage, Chaplain. Look.’

Larger bio-forms were lumbering into view. One was a bloated creature with a huge squirming egg sac hanging beneath its thorax. A pair of towering siege-organisms shambled behind the front line, the smaller organisms scurrying to avoid their massive hooves. One was armed with a pair of enormous claws that looked like they could carve a Rhino in two. The other had one arm deformed into something approximating a wrecking ball, with a mass of spiny bone attached to its arm by lengths of intertwined sinew.

‘Make them pay for every one of your fallen battle-brothers, sergeant,’ said Cassius. ‘I must take my place upon the ramparts. Be ready to move if I call for you.’

As Remas and his men sighted their custom bolters and began raking the xenos with accurate bursts of fire, the Chaplain began to make his way back to the wall. He drew Infernus as he ran, the combi-flamer that he himself had crafted many years ago. It had saved his life on countless occasions. He passed the mid-level squads, who were firing from the wall apertures in disciplined volleys and reloading with smooth, practised movements. Their bolter drill was of such quality that there was barely a pause in the sustained barrage.

It was easy, at first. That was the true horror of the tyranid way of war. Hundreds, even thousands of the enemy died before they even reached the gates of the fortress. The ground was thick with corpses, slick with gore. Once a warrior had emptied several clips and still not come face to face with the enemy, he began to think that the battle was won. Then another wave of alien bodies swept across the ground towards him. And another, and another.

On they came, scuttling over the ruined forms of their fellows, heedless of the storm of fire that swept from the towers and walls of the fortress. Explosive rounds hammered into the swarm, thinning it for scant moments until more pawns scurried into place. Bolter fire picked up individual organisms and hurled them back into the writhing mass, acidic blood splattering, flesh rupturing, smoke rising. Rippling, incinerating waves of white flame marked the impact of plasma cannon fire.

Taking the final stone steps to the main wall four at a time, Cassius burst out into sickly daylight. The sky was thick with tyranid flyer organisms, which were harrying the tight formations of the Ultramarines, swooping down to strike with bladed appendages or strafing them with bursts of vile biological ammunition that bored into armour and flesh. Heavy bolter fire from the fortress towers ripped into the flock of organisms circling above Sigma Fortulis, but seemed to make no appreciable difference to their numbers. Cassius battered a low-flying creature to the floor with his crozius, and opened fire with Infernus to blast several more into chunks of rancid, smoking meat.

Fabian led from the wall, firing bursts from his plasma pistol and hacking away with his power sword. He was a golden figure of hope and righteousness.

Cassius was the merciless, furious angel of death at his side.

‘Hurl them back,’ the Chaplain roared, ‘as Lord Calgar purged their filth from the mountains of Macragge.’

Infernus roared, spewing a hail of hellfire rounds that sent tyranids toppling to the floor, burning and melting as voracious acids ate their flesh. Rushing to the wall, Cassius saw a cluster of warrior-forms that had dragged themselves near to the apex of the wall, using their wicked razor forearms to scale the rough stone surface. Leaning out slightly over the edge, he thumbed the activation stud on his weapon and blanketed the creatures in a curtain of flame. Down they fell, screeching and shrieking, living torches that disappeared into the churning mass at the foot of the structure.

He turned back, and his bionic eye swept across the fortress wall. The air was filled with the dry-metal taste of burnt atmosphere as Brother Praxim fired his plasma cannon, sending great pulses of searing energy blazing through the mass. Next to him Brother Capion’s heavy bolter ran dry. He reached for a grenade at his belt and flicked it live, but a flying organism crashed into him with a clatter of bone and metal, pitching him over the crest of the wall. He hung there for just a moment, armour scraping against the stone, precariously balanced. Cassius leapt forwards to grab him, but too late. Capion fell, and the Chaplain saw the grenade go off in his hand. When the smoke cleared, there was no sign of blue armour.

‘Focus your hate,’ Cassius roared, his anger stoked. ‘Feel the righteous fury of the God-Emperor course through your veins. We are his sword. We are his rage.’

He spun, aimed Infernus, and felt the reassuring kick run down his arm as he blasted another swooping organism from the sky. It wheeled and spun like a stricken fighter jet, and smashed into the inner wall in a spray of gore.

They were taking losses, but the xenos had not breached the walls.

Amidst the continuous thunder of bolter fire, Cassius heard armoured boots clattering up the steps of the inner wall, and turned to see Sergeant Remas and his veteran squad rushing towards him.

‘Chaplain,’ Remas said, and his normally taciturn voice held the faintest hint of excitement. ‘We’ve spotted something. Something you’ll want to see.’

He held out a pair of magnoculars, and gestured towards the broken pinnacles of the highlands to the eastern side of the pass. Cassius took them, and raised them to his organic eye.

Information about wind speed, distance and ballistic drop-off streamed in a column of figures down one side of his view as he scanned the outcroppings. He could make out a dozen or so warrior-forms clambering over the rocks, a difficult climb for a human, and surely a taxing one for the bulky organisms. They were heavy guardian units which combined a solid quadrupedal frame with overlapping plates of dense armour. He knew from experience the punishing firepower that these creatures’ armour could absorb, and knew also that they often placed themselves around potentially vulnerable bio-organisms.

They were there to protect something.

The silhouette of the creature that emerged into view had too upright a posture to be a hive tyrant of the kind that were advancing along the pass below. Each of its four arms carried a blade of bone with an edge of serrated crystal and several clawed sub-limbs ran in two rows along its exoskeletal ribcage. The plates of chitin armour over its back and neck gave way to a sharp face full of a malevolent intelligence no bestial alien of the hive fleets should ever have possessed. Even from this distance the narrowed specks of its eyes spoke of a cruelty almost human in its intensity.

Cassius had seen that silhouette before, at Cold Steel Ridge when it had massacred the honour guard that saved Marneus Calgar from its blades. He had seen that face, that needle-filled grin, at the Battle of the Polar Fortresses, when it had led the charge across those same peaks Cassius had looked out upon from Tigurius’ sanctum.

‘The Swarmlord,’ breathed Cassius. ‘It lives.’

A shiver ran down his spine – anticipation and something colder, more instinctual, that he did not fully understand. Then there was the rage, the searing, hate-filled rage. How many brothers had he seen die at this creature’s hands? Dozens? Hundreds? He pictured Brother Pericos, bisected by a pair of serrated blades. He saw Verrun, roaring his defiance as the creature lifted him up and snapped his neck with what the Chaplain could have sworn was sadistic pleasure.

How many worlds had been devoured because of this abomination? So many dead. So much lost. He could not stay here and waste his bolter rounds on chattel while that monster roamed free.

‘We must kill it,’ said Remas, and it was the first time in many years that Cassius had heard a flicker of excitement in the man’s voice.

‘No. It is too far away, and we have enough to deal with as it is,’ said Captain Fabian. ‘I will not send men away on some doomed assassination mission while the fortress still stands.’

Cassius held out the macrobinoculars and Remas took them. He turned to Fabian.

‘I must kill this thing, brother,’ Cassius said.

‘Chaplain, we need you here,’ protested Fabian. ‘The men need your presence on these walls, your defiance and your strength.’

‘The men are Ultramarines,’ Cassius said. ‘They know their duty, and they will hold. And when I kill this creature, sweeping the rest of the xenos filth from Kolovan will be a far simpler task. It is the key, brother.’

‘It is a distraction. Chaplain Cassius, do not do this.’

‘Hold the walls, captain,’ Cassius said. ‘Hold the beast at bay, and I will cut off its head.’

Without another word, the Chaplain marched down the steps to the inner courtyard, the Tyrannic War veterans at his side. Ultramarine squads who had overheard the exchange glanced at the Lord Chaplain as he passed, but Cassius said nothing, offered no reassurances or even acknowledgment. He could not think of anything else but the desire to meet that foul creature in battle once more, to end its wretched existence. How had it survived? Chapter Master Calgar had torn the creature to pieces in the death-hives of Ichar IV. Cassius remembered every single moment of that cursed charnel pit – fighting through the sludge of digested Imperial citizens, xenos bio-acids eating away at his flesh, dead battle-brothers dissolving in the torrent of filth as he stumbled over their steaming corpses.

All that death. All that sacrifice. And still the beast walked free.

No longer. He would not allow it. He would find it, and he would kill it, for good this time. He would obliterate the creature so thoroughly that whatever foul xenos blasphemy had brought it back to life would never be able to do so again.

‘Our scans of the complex revealed a number of tunnels under the fortress,’ said Remas as they walked. ‘Lava channels, carved out of the earth aeons ago.’

Reaching the floor, they crossed over the inner courtyard, which was ringed by more pagan statues of forgotten gods. At the far end was an archway, and on the right a set of wide, curved stairs led down into the dusty coolness of the catacomb levels. These chambers were narrow and low-ceilinged, and the winding paths and rough stonework suggested that whichever tribe had occupied this fortress had not been overly concerned about burial rites for their dead.

Remas led them past alcoves lined with great stone coffins, placed upright and crudely carved with runes and hieroglyphs from another age. The sergeant made a right turn at an intersection, and they passed through the remains of two shattered stone doors and entered a wide, semi-circular room. The smashed remnants of clay pottery covered the floor, and the walls were scarred in places as if huge slabs of stone had been torn free. In the corner of the room there was a great gouge torn out of the stone floor. Debris surrounding the hole suggested that someone or something had broken into the chamber from below.

Sergeant Remas stepped to the edge, lit a flare and dropped it down. Red light revealed a rough tunnel that sloped gently down out of sight.

‘I’ve no idea who tunnelled their way in here,’ he said. ‘Thieves, perhaps? A creature of some kind? Whatever it was, it carved its way in via a lava channel that runs northwest, towards the mountains where we saw the Swarmlord.’

‘We cannot know that this leads to where we want to go,’ said Cassius.

‘No,’ Remas replied, ‘but geo-scans from the Talassar indicate that there is a series of caverns just to the west of the pass, at the foot of the cliffs. This particular channel leads in that direction.’

‘Perhaps it was an escape route for the fortress defenders?’ suggested Brother Fandralus, staring down into the tunnel, which was barely wide enough for the Space Marines to squeeze through.

‘We cannot cross the open ground to get to our target,’ said Remas, turning to Cassius. ‘We will be swarmed before we get twenty paces. This is our only chance.’

The Chaplain nodded. ‘Lead on, sergeant.’

Sigma Fortulis was a tough old beast. Her walls were thick and strong, and she offered fine firing angles for the warriors defending her. Whoever had carved her out of the earth had known their business, and even thousands of years after her original construction she would have posed a significant tactical challenge for any regular army.

The tyranids were no regular army.

Lumbering artillery-beasts had taken up position in the distance, out of effective range of the Ultramarines’ guns. They vomited forth clouds of explosive living missiles, which arced over the heads of the horde to tear great chunks of stone from the fortress walls. As the battle dragged on, the creatures targeted each of these weak points with barrage after barrage of their spore bombs. Slowly but surely, the xenos carved Sigma Fortulis open. Below, the simple warrior-forms performed their own tasks; eating up the ammunition of the Space Marines. In death they added to the mountain of corpses that reached ever closer to the lower galleries, and to the breaches in the wall.

There was nothing to be done but fight, and the Tactical squads that guarded the lower levels battled heroically to keep the enemy at bay for several hours. Siege organisms barrelled towards them, smashing into the rock with the force of a runaway maglev train. They reached in with their great, hooked forelimbs and strained, tearing stones free, smashing and battering with their heavy, armoured tails. Plasma guns and heavy bolters tore into them in return, but as soon as one fell another charged forth to take its place.

In the end, the deadlock was broken by a phalanx of monstrous tyranid warrior-forms, advanced organisms that fought like seasoned veterans rather than mindless beasts. They carved through the remnants of the Ultramarines’ lower-level defence with wicked, curved blade-limbs, and advanced into the fortress behind a hail of vile bio-organic projectiles that ate through ceramite and flesh with frenzied hunger.

Captain Fabian led the counter-charge from the upper levels. They met the tyranid advance in the cramped corridors of the third level. Bolter rounds and bio-rounds shredded armour and meat as the Third Company Ultramarines hurled themselves into the xenos, roaring their captain’s name. Fabian fought at the tip of the spear, his trusted command squad at his side. He hacked and stabbed with his power sword, firing point-blank into the enemy with his plasma pistol. Around him the Assault squads were relishing the chance to lock blades with their hated foe. Chainswords chewed and crunched through armoured exoskeletons, while power fists grabbed and crushed skulls and limbs. Brother Ollus pushed ahead of his captain to decapitate a snarling monster with a swing of his power axe, then collapsed as another alien fired a sizzling burst of acid into his gut at close range. These creatures were the tyranids’ elite assault troops, far deadlier than the swarming vermin that had launched the assault, but they were outnumbered by Fabian’s force. The last fell to a thrust of the captain’s blade, and Brother Galiun stepped forward to hurl a grenade down the stairway from which the beasts had emerged. It went off with a deep thud, and the screeching coming from the level below went briefly silent.

Captain Fabian wiped rancid alien blood from the visor of his helm. The Third Company had fought brilliantly. He could not have asked anything more from his men, who had made the xenos pay dearly for every foot of ground. They had offered death to the enemy with bolter and blade, felling scores, perhaps hundreds of creatures for every Adeptus Astartes warrior that fell. They had not faltered. He was proud of every one of them.

There was no way they could hold the fortress.

The captain’s eyes scanned the battlefield, the rents that siege-beasts had torn into the walls, the ruptures where tyranid artillery spores had landed, the dead brothers that lined the halls of the fortress. The endless mass of tyranids on the desert ground below, still straining to force their way into Sigma Fortulis, promised no end to the assault. They had thrown back half a dozen waves, but now the rising carpet of dead aliens and the shattered fortifications offered easy access to the fortress proper, and without the fury of Cassius to rally and focus the men, the battle was dissolving into a series of localised skirmishes that were bleeding Fabian’s ranks dry.

Two xenos hauled their way over the wall, and clattered through the mass of corpses towards him. He met the first with a horizontal slash of his power sword, cutting a blade appendage off and slicing deep into the creature’s neck. Edrius charged in and rammed the company banner into the back of the second, pinning it. He aimed his bolt pistol and put a round through the xenos’ skull, ending its mindless screeching. Fabian nodded in appreciation.

‘We cannot hold here, sir,’ Edrius growled. He had taken an acid burn to the throat, and it clearly pained him to speak. ‘They are inside the walls.’

Fabian fired his plasma pistol over the parapet, blasting more climbing xenoforms into ash.

‘I know, brother,’ he said. ‘We have contacted Sergeant Verigar’s force at the landing zone. They are sending airborne extraction. We must hold out until they get here.’

Edrius coughed up blood, cursed and wiped his mouth clean with the back of his gauntlet. ‘Aye, captain,’ he said.

‘Brother Gallus,’ Fabian shouted to his vox operator. ‘Send the word to all squads, fall back to the top level.’

The rampart wall of Sigma Fortulis was wide enough for two Space Marines to comfortably pass each other by, but not for any kind of airborne extraction. The only area where the Third could theoretically do so was the north-western tower, at the only corner of the fort left intact. At both compass points where the wall met the tower, rough stone steps spiralled up to the apex, a wide, roughly circular platform cut with spherical, concentric grooves. They could land a single gunship here at a time, which meant they would have to extract squad-by-squad – hardly ideal, but better than any alternative Fabian could think of.

Below, in the lower halls of Sigma Fortulis, Fabian knew his men were falling back, hacking their way towards the ramparts. It would be hell down there. No longer faced with an effective gun-line, the tyranids would pour into the fortress in horrific numbers, harrying the retreating Space Marines every step of the way.

‘Damn your reckless anger, Chaplain,’ the captain hissed.

With Cassius gone, the Ultramarines had lost a vital tactical edge. Fabian was a fine warrior and an experienced leader, but he could not set a fire in his warriors’ hearts like the Chaplain could. Cassius was an icon, a symbol of the undefeatable, eternal glory of the Adeptus Astartes. He had been purging the enemies of mankind for centuries before Fabian was even born, had held back the tyranid tide on a hundred worlds. His mere presence was enough to convince the men that they would destroy any force sent against them – how could they possibly fall, with the legendary Master of Sanctity at their side?

Now he was gone, the thick walls of Sigma Fortulis felt like scant protection indeed.

‘Second and fifth squads, hold the stairs,’ he roared, rushing alongside his men to the northwest tower. ‘Keep them clear. The rest of you, sweep the walls and the skies. Devastator squads to the top of the tower.’

The heavy weapons teams lugged their bulky weapons up the winding steps of the tower, and set up behind its shallow crenellations. The spine-shaking thud of heavy bolter fire began afresh, joined by the roar of plasma and flame. By now the tyranids had scaled the eastern wall in force, and they swept across the ramparts towards the repositioned Space Marines. Once again the Ultramarines had a solid defensive position, with Tactical squads kneeling to the fore and the blistering fire of the heavy weapons teams screaming overhead. Warrior-forms leapt and ran at the ceramite wall, but were torn to shreds by the enfilade. The xenos flyers had more success, and their bio-organic weapons dropped several Space Marines to the ground, smoking craters burned through their armour, but the creatures’ numbers had been severely culled by concentrated fire.

The sun dimmed, as if it too was being choked to death by the climactic torture that the tyranids had unleashed upon Kolovan. Suddenly it was the dusty beige of late evening, then the near pitch-black of night. Dull, grey snow fell across the carnage, blanketing the proud blue of the Ultramarines and the foul milky yellow of the xenos swarm in a layer of filth. Not snow, Fabian realised. The first ash clouds from Galenus’ detonation had arrived, thick enough to blot out the sun. He blinked on his helmet’s night-vision filter, and winced as he fired a burst of white-hot plasma into the midst of the enemy that briefly lit up his view like the aftermath of a nuclear explosion.

Tactical squads poured out of the lower level access stairs, taking their place in the Ultramarines line with barely a pause, and then turning to add their own volleys to the barrage. Fabian felt a surge of pride as he watched them, the finest warriors in the galaxy, still calm and disciplined in the face of this chaos.

Their proud defiance would not be enough. More and more warrior-forms poured over the wall, and finally the advance reached blade range. No longer able to pour fire into the enemy, the Ultramarines were forced to switch to combat knives and other close-range weapons instead. Fabian pushed to the front, leading with his power sword. In the frenzy of the press, all thought of finesse or weapon-art was abandoned in favour of blunt, mechanical killing. He skewered one creature through the mouth, wrenched his blade free and carved a bloody line across the torso of another. He punched, smashed with the pommel of his blade, stomped a fallen xenos under his boots, spun and intercepted a thrusting bonesword, and hacked his blade into the owner’s cranium in a spray of ichor.

Bio-rounds slammed into his pauldron, staggering him, and a shrieking warrior-form leapt upon his back, blade-limbs digging at his warplate, trying to find a weak point in the fine ceramite. Brother Edrius leapt in, thrusting his combat knife into the thing’s side and dragging it to the floor, despatching it with practised thrusts.

‘My thanks, brother,’ said Fabian.

Edrius nodded, lifting the company banner high into the air, where it was met with a furious cheer. They were retreating here, thought Fabian, but no shame would fall upon his beloved Third Company.

Something tall and unthinkably fast hurled itself over the wall and flashed towards Edrius, sending torn Ultramarines reeling behind it as it came.

There was the hissing rush of something incredibly sharp being propelled through the air with tremendous force, and a strangled gasp from Brother Edrius. The standard bearer turned to Fabian, eyes wide in surprise, and the right half of his upper torso slid free, cut at a perfect diagonal. The rest of his body swayed a moment, and then toppled back into the arms of the Space Marine behind him with a splatter of gore.

In the fallen Ultramarine’s place stood a creature of nightmare. Its eyes, twin orbs of pitiless black, were buried under a sweeping head-crest that daggered backwards, tipped with bony spikes and ridges. Its gaping maw was filled with row upon row of needle-sharp teeth, through which a vile, purple tongue protruded, tasting the air. The body was a towering mass of corded muscle and chitin. Each limb grasped a bio-weapon, a writhing, tendon-like lash tipped with cruel barbs in the right claw, a serrated bonesword in the left. Two lower arms clutched a vicious-looking gun-organ, which pulsed with energy.

The very presence of the creature seemed to inspire the xenos around it into a frenzied rage. They shrieked as one, and hurled themselves at the Space Marines with renewed vigour. As they surged forward, so did the beast, rushing at Fabian with its whip leading the way. The captain batted the weapon aside, but it curled around his blade and scored his plate at the side, not enough to breach the armour, but with force enough to send him staggering sideways into the thrust of the creature’s bonesword. At the last moment he pirouetted to the right, letting the weapon scrape past him, and returned with a thrust aimed at the beast’s lower torso. It turned as well, with grace that seemed absurd given its horrific, muscle-bound form, avoiding the strike by the barest of margins.

Fabian set his feet and charged in again, accepting another lash from the creature’s whip and pushing the beast’s blade out wide with his own weapon, then coming back across with a backhand cut that sliced the gun-organ in half in a spray of ichor and bone fragments. The creature shrieked, reeled backwards, and Fabian saw the opening. He lunged forward, tip of his blade seeking the beast’s armoured chest. It was a kill-thrust, aggressive and viper-quick.

The tyranid anticipated it. As Fabian lunged, it stepped back with unnatural speed, and the captain realised in shock that the creature had desired his strike, had baited him into it. The tendril lash wrapped around his sword arm, overextending his motion and dragging him forward to stumble on the blood-slick ground. He landed on one knee, disorientated. The bonesword came down. Fabian twisted to the side, but still it cracked into his helm, slicing through the ceramite with ease, carving into his face.

Agony lanced through his skull. His vision exploded, helmet sensors destroyed by the strike. Light blinded him, then darkness fell over him. He had no idea where he was, where his enemy was. He rolled to the side, desperately, and heard the shriek of something hard scraping stone. With one hand he pulled his ruined helm free. Something came with it, something wet and organic. Fabian gasped in agony. Something wrapped around his throat, digging into his flesh, and he felt himself being dragged to his feet.

Suddenly there was light. Not the fluorescent green of his helmet’s night-vision, but a harsh and searching glare that ached at his left eye. For some reason it did not reach his right. The sun had come back, he thought, blurrily. There was a sound too, a deep, throaty scream backed by a mechanical thud-thud-thud. Dimly, as if through a cloud of muddied water, he saw the xenos clutching him turn its hateful stare to the skies, and he heard it offer its own roar of outrage.

He grabbed at his belt, felt his fingers close around a small, metal disk.

The creature looked back at him, dragged him closer until he could smell its reeking, spoiled-meat breath, and brought its blade back to strike.

Fabian punched his clenched fist through its hideous teeth, burying his gauntlet in its throat. The metal disk he clutched in that gauntlet gave a slight, electronic trill muffled by the enveloping flesh.

Then his world erupted in fire.

Chapter Four

After several hours of winding their way through the confines of the lava channel, Cassius and the veteran squad broke through into a twisted, cramped series of conduits bisected by great pillars of igneous rock. These immense shafts glistened in the bioluminescent light given off by great swathes of fungal growths draping the walls. The soft blue glow they emanated revealed a twisting stair carved into the largest of these pillars, winding its way towards the surface.

Ascending the stairway carefully, for it was hardly designed for the staggering weight of a Space Marine in full warplate, they passed through another slowly rising chamber. At the far end was a boulder set into a series of grooves, cleverly designed so that a team of humans could have hauled it clear. Cassius shifted it aside with ease, and hazy yellow light seeped into the hollow, along with motes of drifting ash.

‘Well done, sergeant,’ he nodded, as the squad filtered out into the dull glare of Kolovan’s sun.

They had emerged roughly a thousand metres from the fortress, in a sheltered nook to the west of the canyon pass that masked their position from the main xenos force. The air was so thick with the miasma of alien spores accompanying the tyranid horde that the filter of Cassius’ rebreather unit was struggling to keep up. The noise of battle behind them was deafening, the high-pitched screech of the alien horde blending with the rhythmic thud of impacting bolter shells and the throaty roar of heavy weapons fire.

‘We should be below the Swarmlord’s last confirmed position,’ said Remas, already holstering his bolt pistol and reaching for a solid handhold. ‘We must make haste as we’ll be exposed as we climb.’

The slope of shattered rock was formidable. Soldiers of the Astra Militarum, even specialised reconnaissance troops, would have been hard-pressed to make the climb. The Ultramarines were tireless. They did not glance back as they climbed with weapons slung. Even Covellos kept pace, his grav-cannon clamped to his back. Cassius led the way and where he could not find a grip, he splintered the stone beneath his fingers to make his own.

The Chaplain paused in his ascent. He swung onto a roughly horizontal ledge and planted his feet, then held his combi-bolter up to his bionic eye, scanning the slope above him.

‘Move on, brothers!’ said Cassius. ‘Do not tarry. We will not remain unseen for long.’

In the valley below, the thump and chatter of bolter fire reached his ears. He risked a backwards glance. Fresh waves of warrior-organisms reached the close bolter range of the defending Ultramarines, and vanished in bursts of gore and shrapnel. A missile streaked from the upper galleries and struck the forward limb of an artillery-beast. It toppled forwards, its huge back-mounted bio-cannon discharging directly into the ground in front of it, sending a plume of dust and foul alien blood into the sky.

Finally, Cassius reached the top of the slope, emerging on a small ledge of broken rock. In front of him the ground rose once more, but it was a gentle bank of no more than a few metres. He drew his weapons, and scanned the immediate environment while he waited for the veteran squad to join him. He saw no movement, but he felt a shiver of anticipation run down his spine. They were close, he could feel it. Centuries of battle had gifted Cassius with an almost preternatural combat sense. Remas and his men clambered over the edge and drew their weapons.

‘We draw near,’ said Sergeant Remas. ‘I can smell the foulness of the enemy from here.’

‘Beyond that rise,’ said Brother Covellos in a hushed voice, gesturing forwards. With guns held at the ready and blades drawn, the Tyrannic War veterans went to hunt their prey.

It did not take them long to find the enemy. The next shallow rise of loose stone opened onto a wide plateau. Curved spars of stone, like broken ribs, reached towards the discoloured sky. Raptors’ nests formed black knots of dried leaves and debris. Between the uprooted slabs of rock lumbered the Swarmlord’s guard, each one a mobile fortress of muscle and bone. Their mouths were locked in a savage grin beneath armour plating akin to the visor of a helmet, and they walked on four legs, carrying a symbiote gun in their forelimbs. The weapon was a fleshy tube that ended in a lipless mouth clamped around a spine of ridged bone. Cassius counted half a dozen ranged across the plateau, sensor-pits beneath their jawlines opening and closing as they searched for the approaching Ultramarines.

One of the creatures bellowed, and the low rolling sound seemed to shake the stone around Cassius. The other xenos replied with braying calls of their own and began to stalk towards the veterans’ position.

Cassius ducked into cover as the other veterans spread out around him. Covellos backed against a slab of rock and hefted his grav-cannon, the servos of his armour whining as they compensated for the weapon’s weight. Eight pairs of eyes fell on the Chaplain, waiting eagerly for the signal to engage the hated foe.

‘On the slopes beneath the northern fortress of Macragge, you saw it!’ called out Cassius as the hive guard advanced. ‘You, Etriades, and you, Fandralus. You were there. And Brother Covellos, you witnessed the depravity of the tyranid in the hive cities of Genestus! Here is where you claim your revenge. With me, brothers, for Macragge and for Sotha!’

Cassius knew what drove every one of the Ultramarines alongside him. He knew how to hit the nerve that would spur each of them on. Cassius led the charge and the veterans followed him, with Etriades sprinting, twin chainswords out, as if racing Cassius to reach the enemy.

The veterans fired as they ran. A volley slammed into one hive guard, blasting chunks from the chitin protecting its head.

One hive guard stood proud of cover and levelled its weapon. A split second later a zone of warped gravity imploded around it, crushing its exoskeleton and pulping the muscle and organ within. One side of the creature was squashed into gory shreds by the blast of Covellos’ grav-cannon, and it slumped, oozing gore, against the rocks.

‘They crumble before our fury!’ cried Cassius.

The hive guard counter-charged. Etriades jumped and kicked off a spur of rock, crashing into one, blades first. Cassius followed Etriades in as the hive guard pivoted to throw off the Ultramarine. Etriades hacked at the tyranid but the chitin armouring the creature’s leg turned aside the worst of the blow. The guard stamped down on Etriades’ leg and bowed down over him with its jaw yawning wide.

Cassius drew back his crozius arcanum and swung it down at the hive guard as its head was turned from him. The weapon’s head crunched into its shoulder and the power field erupted in a flash of light and thunder. The chitin was blown open, revealing slabs of seething muscle inside. A jet of vaporised gore spurted from the wound and Cassius was momentarily blinded. He fought on instinct, ducking the expected return blow from the barrel of the hive guard’s cannon and driving his fist up into its jaw.

The tyranid fell back, roaring. Etriades rolled from beneath its hoof and stabbed both blades up into its torso. The blades chewed in between the exoskeleton ribs and plunged deep into organ and muscle. The tyranid threw its head back and howled as gore bubbled up between its jaws.

Cassius brought the crozius down into its face. The creature’s lower jaw was ripped open and the split ran down to its breastbone.

Etriades ripped his chainswords free and rammed both into the gory mess that remained of the tyranid’s mouth. The chainteeth sawed deep into its brain.

Cassius glanced behind him to size up the rest of the fight. Another hive guard was down from the veterans’ combined bolter fire. Brother Vetrius and Sergeant Remas were tackling another, and Remas’ power sword had already hacked off one of its forelimbs. The squad was forcing back the monsters, breaking up their line and engaging them face-to-face.

From the corner of his eye, the Chaplain caught a glimpse of pale flesh. One of the xenos aimed its vile weapon through the gap between two stone spires. Instinct sparked Cassius to movement, but he was nowhere near quick enough to cover the ground to the creature before it fired.

The quivering mouth of the cannon spat the spine of twisted bone across the plateau. Cassius followed its path as it arrowed towards where Brother Covellos was lining up another shot from his grav-cannon.

The spike impaled Covellos through the chest and pinned him to the slab of rock behind him. Blood welled up from the split and buckled breastplate. The grav-cannon fell to the ground at Covellos’ side and his hands opened and closed convulsively.

‘Brother!’ yelled Vetrius. He left Remas’ side and ran for his fallen squadmate.

‘Press on!’ yelled Cassius. ‘Break the line! Break their will!’

If the squad stopped here to finish off the hive guard, they would never achieve their objective. They had to hit hard and fast, before the tyranids regrouped and brought more warrior-forms to bear.

Cassius and Etriades ran at the hive guard who had slain Covellos. Cassius doused it in flame as it tried to aim at Etriades, and in its moment of confusion and pain Cassius was upon it. He battered its gun aside with one blow of his crozius and shattered its jaw with the return stroke. Etriades dived into the burning tyranid with all the reckless fury the xenos stoked in him, ramming his chainblades over and over again into the abdomen of the hive guard where the exoskeleton gave way to a stretch of vulnerable skin.

‘You four with me,’ shouted Cassius, gesturing to Remas, Etriades, Vetrius and Fandralus. These were his best fighters, his hardiest souls. ‘The rest of you, finish the guardians.’

Beyond the hive guard line, watching the battle in the valley below, was the towering four-armed shape of the Swarmlord. This close it was even clearer what an aberration the creature was. Its colours were a dark and mottled version of the hive fleet’s colouration, and it was covered in scar tissue and encrusted growths as if it had been dredged up from the bottom of an ocean. Its four boneswords, each longer than a Space Marine was tall, were covered in deformed eyes and edged with fang-like growths of organic crystal. It had a lean, ancient look, as if time had winnowed out all the unnecessary tissue and left it composed of pure muscle, bone and malice.

A rank, spore-heavy haze hung around the Swarmlord, spurted out by the vents emerging from the chitin plates along its back. It let out a low clicking purr as it turned from the battle below to face Cassius, and its eyes narrowed as it focused on the Chaplain.

The Swarmlord was not just another alien menace. It was not just a lightning rod around which the tyranid swarm gathered. It was the herald of oblivion. It had appeared on a hundred worlds across the galaxy, always at the head of a rampant horde that swept all before it. It was clever, appallingly so, capable of surprising even the most brilliant tactical minds of the Imperium. At Macragge it had outmanoeuvred even Marneus Calgar, the heir of Guilliman’s strategic brilliance.

And it was supposed to be dead.

‘I recognise you,’ said Cassius as he moved carefully across the broken ground, describing a wide circle around the Swarmlord. Its boneswords gave it a huge killing edge and Cassius stayed just out of range. ‘I saw you fall at the Battle for Macragge. We killed you once. And when we have taught you how to fear, we will kill you again.’

The sounds of battle from behind Cassius seemed very far away as he focused on the Swarmlord. Its face split in what looked very much like a grin, the sharp mandibles on either side of its jaws sliding back to reveal dozens of knife-like teeth. It spun two of its blades like a duellist limbering up their sword arm, and joints clicked and popped as it shifted its weight. Its long, scaly tail slithered as it passed over the rocks.

Cassius didn’t take his eyes off the towering xenos as he swapped out the magazine of his bolter. He slid in a new one, this one only half-full because the shells inside were manufactured by a precious few archaeotech crucibles of the Adeptus Mechanicus.

Sergeant Remas reached Cassius’ side along with Brother Etriades. Etriades’ chainblades were already smoking with the effort of the motors sawing through chitin and muscle.

‘We fight this thing as one,’ growled Cassius. ‘Temper your rage with caution, Etriades. I have seen too many brothers fall to those blades.’

The Swarmlord growled, shaking the ground. It advanced a half pace and Cassius dropped back in response, maintaining the gap.

Brother Fandralus reached Cassius’ position. His armour was badly scored, and he reloaded his bolter as he shook the worst of the gore from his faceplate. Fandralus was as tough as they came; the hive guard had failed in their best efforts to bring him down. Vetrius took the creature’s left flank, hefting his chainsword.

‘Our actions here will decide the fate of this entire sector,’ Cassius continued, circling the creature slowly. ‘This is a glorious moment. The Emperor sent us here to serve His justice, and we will not be found wanting.’

The Swarmlord crouched down and bellowed. The sound was like a shrieking gale that blew hot and damp across the plateau. Cassius levelled his combi-bolter at it and it swayed to the side, extremely agile for a creature of such size.

‘In the name of the primarch, and for every loyal Imperial soul this filth has claimed,’ said Cassius, raising his crozius into the air, ‘take its head!’

It was Etriades who moved first. Cassius knew he would – he could not be held back from a fight. In a line battle that was a weakness that needed addressing, but here his fury would be required; they had to keep the creature busy on all sides, off-balance and reeling.

It was easier said than done.

The Swarmlord rushed forward and its four blades swept out. Vetrius’ neck opened, spraying crimson, and a trailing blade tore across his gut. He fell, pawing at his neck, gasping. Etriades leapt and swivelled, throwing himself between the scything blades to land inside the alien’s guard. The Swarmlord spun on its back leg, again far quicker than its bulk seemed capable of, and its muscular tail slammed into Etriades, sending him flying through the air. Stone splintered as he crunched to a halt a few metres from the edge of a sudden drop into the valley.

Fandralus rattled off a volley of bolter shells into the Swarmlord. The xenos barely noticed the explosive impacts along its back carapace but it threw a hate-filled glance in his direction. It was just enough to distract it as Cassius and Remas rushed in.

Remas fired as he went. Again, the bolter shells barely scratched the layers of impacted chitin. Remas leapt over a bonesword that whipped towards him at knee height, but he immediately had to dive face-first to the ground to avoid another that almost sliced off his head. A third cut down and Remas rolled out of the way.

The Swarmlord was focused on Remas. That was their advantage – for all its strength and fury, the Ultramarines outnumbered it. It was truly rare to corner such a creature alone, and that gave the squad an equally rare opportunity to kill it. Cassius ran at it, holding his fire, and brought his crozius down in a crushing overhead blow.

It would do no good to strike at its torso or head. What the lightning-quick boneswords did not parry, the layers of chitin would turn aside. Instead Cassius aimed low, at the muscle and exoskeleton of the Swarmlord’s upper back leg.

With a burst of light, the armour of its thigh was torn open. Hard shrapnel pinged against Cassius’ armour. The muscle packing the Swarmlord’s leg was laid gorily open and the monster howled.

‘Fine strike, Chaplain!’ yelled Etriades. He assaulted the Swarmlord again, and it swivelled to face him. Its mouth split wide open and it bellowed at Etriades as it parried another of his sword-blows with supernatural speed. The vents along its back spat a grey-green spore fog that cast a foul shadow over the plateau, as if night had suddenly fallen on Kolovan.

A counter-stroke from the Swarmlord caught Etriades on his shin and the resonating crystal sliced right through ceramite and bone. The warrior was pitched onto his back with his foot and lower leg sailing over the edge of the plateau. The severed portion tumbled down towards the seething mass of tyranids.

Etriades gasped in pain and reached for the bolt pistol mag-clamped to his thigh.

Cassius rolled out of the way of the Swarmlord’s blades, behind the creature. Its tail sailed over his head. He aimed at its wounded leg and fired his combi-weapon’s nozzle, dousing the limb in clinging fuel. Exposed muscle burned and the xenos buckled onto one reverse-jointed knee as the flames clambered up its back and ribcage.

Bolter shells pinged off the Swarmlord’s carapace. Etriades’ and Fandralus’ fire was accurate, but achieved little more than to annoy the creature. The Swarmlord learned quickly, and it had identified the Chaplain as the greatest threat. It cast Fandralus aside with a disinterested backhand swipe that tore through his armour, and focused now on Cassius.

It did not lunge at the Chaplain with its blades or try to crunch down on his body with its fangs. A flicker of power burst into life in front of its face, between its unblinking eyes. Cassius had just enough warning from the familiar sensation of greasiness and static to dive for cover and shield his mind as much as his body.

Warpcraft. He had faced the assaults of enemy psykers so many times he had written whole volumes of addenda to the Codex Astartes on the perils of the witch. Eldar farseers had tried to flay his soul from his body and sorcerers pledged to the gods of the warp had sought to boil his blood or immolate him with the power of their minds. He had trained with the Librarians of the Ultramarines, including the peerless Tigurius himself, to resist the effects of the psyker’s arts on his mind and body.

Cassius’ gambit had worked. He had wounded the xenos and caught its attention, and now it would attempt to scour his mind. But Cassius’ spirit was as strong as that of any Space Marine who had walked the Imperium since the Horus Heresy, and the Swarmlord would find its psychic power was not as irresistible as it thought.

Cassius had heard the creature’s horrific scream from a distance before, echoing between the polar mountains of Macragge. It was a brute-force assault that drove a psychic spike into the mind of the target, shattering its brain functions and leaving it a soul-dead husk. Cassius had never experienced it first-hand until now, and he ran rapidly through a mental shielding prayer as the rising shriek of the Swarmlord’s will rose in his mind.

From the Kraken and the daemon, from the traitor and the heretic, from those without, those within and those beyond – my Emperor, my primarch, my brethren living and dead, deliver us.

A white-hot spear of sound impaled Cassius. The pain burst in his mind and black spots flared before his eyes. He felt himself falling.

Pain was nothing. A Space Marine did not fear it – he did not fear anything. But the loss of control was abhorrent. The thought of being rendered helpless was so offensive that Cassius took hold of that rage and clung to it, splitting the conscious part of himself away from the substance of his brain overwhelmed by the assault.

He rode it out. A lesser mind would have been consumed, but Cassius, the Master of Sanctity, had been conditioned and counselled by Lord Tigurius in the mental discipline required by a Chaplain of the Space Marines.

The spike was withdrawn. Cassius poured his fury, his faith, everything that was key to his soul, into the breach it left behind. His body lay on the rocks of the plateau, taut with convulsions. His fist had clenched reflexively around his crozius, and he snatched the combi-bolter from where it had fallen on the rocks beside him.

The Chaplain hauled himself upright, forcing back the complaints of his strained body. The Swarmlord had turned away, assuming Cassius was dead, to finish off Etriades who was picking himself up with one shoulder guard badly buckled and one leg a mangled stump.

The Swarmlord paused. Its sensor-pits flared. But Cassius was even faster than the tyranid’s alien reflexes. He blasted a trio of shots into the side of its face. The bolts were not the standard ammunition of the Adeptus Astartes, but hellfire rounds, created by the alien hunters of the Ordo Xenos. Their explosive cores had been replaced with reservoirs of molecular acid created to react with the tyranid physiology and burn through their chitin and flesh like the flame of a cutting torch. The side of the Swarmlord’s face disintegrated, revealing the sensor-pit channels riddling its skull, and for a moment one eye socket was eaten bare to echo Cassius’ own scarred face.

Cassius dived in closer and smacked his crozius against the side of the Swarmlord’s grinning skull. The power field tore through muscle and bone in a flash. The alien’s head cracked to the side in a burst of shattered teeth. Its lower jaw was half torn from its face and hung by a flap of skin, spraying gore.

The Swarmlord dropped to one knee, stunned. Cassius swung his reverse blow up into its throat and felt the crunch of its exoskeleton fracturing. Remas leapt at the creature, leading with his power sword. With the tyranid’s guard down, it was vulnerable. The blade ripped into its chest. Fandralus was next in, pouring bolter fire into the Swarmlord’s shattered face despite the appalling wound that had opened his breastplate horizontally. Brother Tiresis was next in, fresh from breaking the line of hive guard, swinging his power axe into the Swarmlord’s wounded leg and burying the blade deep in the muscle.

The rest of the squad caught up with Cassius’ group, bolters freshly reloaded with hellfire rounds. As the Swarmlord weaved its blades around to fend off the melee assault, the Space Marines opened fire from all sides, enveloping the hated creature in a blistering storm. It screeched, staggered and slumped to the floor in a defensive crouch.

Sensing that the battle was nearing its end, Fandralus drew his blade and rushed in at the monster’s unguarded flank.

‘Die, damn you!’ he shouted as he ran, gripping the sword two-handed, tip pointing at the ground. He raised the blade, aiming to drive it deep into the stricken beast’s flank.

The Swarmlord reared up, blood spraying from the countless wounds the Ultramarines had opened on its body. It swept its upper pair of boneswords across in a lateral slice, blindingly fast. Fandralus came apart, bisected at the waist with surgical precision.

But the Swarmlord had lowered its defences to kill. More bolter shells poured in, opening fresh wounds in the creature’s charred and mangled exoskeleton. Someone hurled a grenade, which exploded an inch from its face, cooking flesh and blasting a chunk of its shattered jaw free. Cassius kept Infernus level, washing the creature with cleansing flame. The stench of burning matter was almost unbearable. The Swarmlord threw its ruined head back and bellowed so loudly the sound echoed back and forth around the valley below like the sounding of a terrible war-horn.

The sound returned from below, this time the howling of thousands of tyranids. As if in mourning, the entire horde cried out, from the high screeches of the termagants to the deep lowing of the siege-organisms. It was the sound of anguish and pain distilled, the desolate wail of the hive mind recognising the suffering of its deadliest avatar.

‘No pause!’ yelled Cassius. His head still rang from the psychic assault and the edges of his vision were greyed out, but he forced on through the pain. ‘No quarter!’

Cassius felt the humming in his hand as the crozius’ power field flared back into life. He ran at the Swarmlord and leapt, trusting in the pain and confusion of the creature to keep it from hitting him with another swipe of its boneswords. His crozius fell in a high arc and slammed into its face above its ruined left eye. It split the skull clean open and in a flash obliterated everything from the creature’s forehead to brain stem. The xenos reeled and crashed to the floor.

The veterans moved in, firing the last of their hellfire ammunition into the creature’s vital organs, making sure that it was well and truly dead.

Cassius let the pain in his head ebb away as he looked upon the corpse of the terror of Macragge, the avatar of the hive mind. His armour dispensed painkillers into his bloodstream and his head cleared slightly, though he still felt the oily, nauseous aftermath of the psychic intrusion.

It was dead. He stared at its ruined features, and tiredness battled with relief for mastery of his battered soul. He thought of all the brave sons of Ultramar that had fallen at this monster’s claws, remembered the horror he had felt when it had downed Marneus Calgar. The Chapter Master had never been quite the same since that day. Still glorious, of course, still the greatest hero of the Imperium and the unmatched warrior he always was, but colder and slower to smile. He had left something behind on the blood-slicked ice of Macragge. Another reason to hate the tyranids. Another reason to celebrate the death of this monster. And yet Cassius could not.

There was no flare of triumph in the Chaplain’s mind. Perhaps, had he been younger, he would have felt it and grasped it, and sermonised on the glory the veterans had just earned for their Chapter. He would have reflected on how the history of the Imperium had been changed by the actions of the squad that day. But now, the needs of the battle still being fought weighed too heavily for him to give those thoughts the time to form. The day was not over yet.

Cassius turned back to his squad, who had gathered around the Swarmlord’s corpse. Etriades was leaning against a rock, pale and exhausted but with a triumphant smile on his face. The Chaplain rushed to his side. The veteran’s transhuman biology had already clotted the blood in his severed leg, but a score of other wounds were starting to take their toll. Etriades would require urgent medical attention if he were to survive.

‘It is done,’ said the Chaplain. Behind them the Swarmlord was a mass of torn organs, severed limbs and scorched matter. The stones glistened with ichor. ‘You have earned great glory today, brother. Now hold on, and we’ll get you to an Apothecary.’

‘I’m done, Chaplain,’ Etriades said, through a mouthful of blood. ‘I’ll just slow you down. Leave me here with a bolter, and I’ll cover your retreat.’

‘Enough,’ snapped Cassius. ‘Talk such foolishness again and I will have you doing penance for the next hundred years. You’re coming with us.’

As Brother Tiresis helped Etriades up, the Chaplain walked to the edge of the pass and looked down. The tyranid mass had not halted with the death of the Swarmlord. Sigma Fortulis would not hold much longer. In the bloody quagmire that had built up beneath the fortress, hundreds of warrior-forms were swarming over the heaps of their dead. A hive tyrant had survived the volleys of the Devastator units above and was marshalling the lesser organisms forward, and already a living ladder of writhing bodies had formed as they clambered up the sheer rock to reach the lowest galleries. Bolter fire stuttered down ceaselessly in a waterfall of shrapnel that sliced and tore the tyranids apart, but it was not enough to stop them from forcing a breach.

‘Take the corpse of Brother Covellos,’ continued Cassius. ‘There is no time to mourn our lost, nor to savour our victory. Our battle-brothers need us. The swarm does not relent.’

‘Chaplain!’ came the voice of Brother Kilrian. ‘They cut off our retreat!’

Cassius ran to the scree slope and stared down. Hundreds of warrior-forms were clawing their way towards the veterans, far too many to fight with their depleted numbers. The creatures hissed and shrieked as they came, black eyes locked single-mindedly on their quarry.

‘This way,’ said Sergeant Remas, pointing away from the pass, into the jagged rocks of the lowlands. ‘Move!’

They ran, trying to put as much distance between themselves and the xenos dragging themselves up the slope as possible. Cassius looked for any sign of cover, of a path that could lead them around and away from the tyranids, but could see nothing. The ash continued to fall, obscuring their vision. It was thick on the ground now, and caked the Ultramarines’ armour. He could see flashes of gunfire back towards the fortress, but all else was swirling dust and smoke. Only his bionic eye could cut through the gloom, and it saw nothing but pitiless rock in all directions.

Ahead there was a flat, wide ridge of broken earth, lined with boulders. Remas scrambled up in the lead, and cursed as he glanced over the edge. Cassius saw him raise his bolt pistol and fire, and knew they were outflanked. With Etriades injured and Covellos’ body in tow, they could not outrun the enemy. All that was left was to send as many of the enemy with them as they could.

‘More xenos filth to purge!’ he said. ‘Time to earn your place at the God-Emperor’s side, Ultramarines. Let them taste the fury of Macragge!’

The veterans roared their defiance as they took position on the ridge, slamming into cover behind boulders and raking the onrushing tyranids with bolter fire. The ash was thick now, and masked the exact numbers of the enemy, but they rushed in from all sides, hurling themselves at the remaining Space Marines. Etriades leaned against a rocky spur, blasting into the mass with his bolt pistol. His arm swayed as he fired. He had lost a horrific amount of blood, and Cassius doubted he would last much longer.

‘One last triumph, brothers!’ the Chaplain bellowed. ‘One last glory in the primarch’s name!’

More and more tyranids raced across the ground towards their position. Cassius turned to the nearest cluster of aliens, which leapt and scrambled towards him across the broken earth. Infernus spat a tongue of fire, and two of the creatures went down, wreathed in flames.

He wondered whether Fabian still held the fortress. He had thought the death of the Swarmlord would disrupt the invasion. He had counted on it, and it had not happened. Cassius was not a man given to second-guessing, but a voice in the back of his head wondered if he had made the right choice.

He swept his crozius around, shattering the armour-plated hide of a warrior-form, then unleashed a torrent of bolter shells from Infernus that ripped through a throng of blade-armed monstrosities. He turned and saw Sergeant Remas fall, sent spinning to the floor by a hail of biological projectiles. Cassius rushed towards him, battering alien forms aside with his crozius.

‘Sergeant!’ he cried.

‘I’m fine,’ Remas said, through gritted teeth. He raised his pistol and fired past Cassius, and the Chaplain heard the wet thud of an impacting bolt round.

More projectiles struck Cassius, driving him to his knees. He felt an angry burn in his side, and knew that at least one had penetrated his plate. On all sides the tyranids pressed in, clambering over their dead, desperate to spill transhuman blood. Cassius continued to shatter limbs and skulls with his crozius, but it was becoming harder to find space to swing. Jaws snapped at his face, and he grasped the lower mandible, squeezed and wrenched, and felt a satisfying crunch. He pushed the screeching creature away and turned to meet a new threat on his right.

Something clubbed him in the chest and pitched him on his back. Infernus slipped from his hand, skittering away on the loose rock. Dazed, he looked up into the coal-black eyes of a towering beast with curving, serrated blade-limbs. It leered at him, tongue lashing out to taste the air.

Light washed over its maggot-pale flesh, and it hissed and looked up to the left. Cassius stretched, his fingers clasped the grip of Infernus and he raised the combi-weapon.

There was a rattling roar, and the creature’s torso exploded in a shower of sickly yellow ichor. It toppled to the side, and as it fell a score of creatures behind it also exploded into gobbets of flesh and shards of bone-plate.

Roaring overhead came three blessed gunships of the Fifth Company, assault cannons blazing. Huge swathes of tyranid warrior-forms were simply evaporated in the barrage, sending clouds of bloody mist swirling into the sky to mix with the choking ash. The Stormravens turned a tight circle and swung back around, slowing to hover several metres behind the squad, in the open ground behind their position.

Searchlights lit up the ground, and Cassius could see Ultramarines pouring from the access doors to set up defensive perimeters around the vessels.

‘Up, brothers!’ he roared, scrambling to his feet and dragging Remas along with him. ‘The Emperor has use for us yet!’

While the Ultramarines poured accurate, punishing suppressive fire into the stunned and reeling tyranids, the veteran squad rushed towards the safety of the gunships. Corvellos’ body was lost, but Etriades was being carried by two of his brothers. He was barely conscious, and his head lolled worryingly, but his eyes were still open. The defensive circle opened to let them pass, and Cassius hauled Remas into the lead gunship’s transport hold, where he staggered against the far wall, wincing in pain. The rest of the veterans followed him in, and the floor swayed beneath them as the ship lifted into the sky, engines screaming.

‘Tell me you at least killed the damned thing?’ came a rasping voice from the back of the transport bay.

Captain Fabian stood there, an Apothecary tending to the jagged latticework of scars that encircled his neck. That was far from his most prominent injury; one side of his face was a ruin of seared flesh and weeping fluid, and his left hand was gone. Two members of his command squad stood at his side. One clutched the tattered, bloodstained but unbroken banner of the Fifth Company.

Cassius looked at him for a long moment.

‘We did, captain,’ he replied.

‘The fortress fell regardless,’ Fabian said. ‘I lost many good men today. I hope it was worth it, Chaplain.’

Cassius said nothing. The captain waved his Apothecary away and gestured for him to see to the stricken Etriades.

‘There is news from Sergeant Verigar at the landing zone,’ said Fabian, still staring at the Chaplain through his one good eye. ‘The Adeptus Mechanicus have made contact. They claim to know a way to weaken the hive fleet’s grip on Kolovan. We may have a genuine way to defeat them after all.’

Chapter Five

In the time since the Third and Fifth Companies had last seen the landing zone, Sergeant Verigar’s men and the scores of servitor menials that had transferred down from low orbit had certainly been busy. The base camp had spread out across the desert, a wide outer circle of sentry turrets and portable defences securing the approach on all sides. Fifth Company Tactical squads had taken up position around the perimeter, and they cheered as the returning Stormravens of the Third circled in to land in the centre of the camp. Everything was blanketed by a layer of grey ash, so thick that the Ultramarines’ boots left huge prints behind as they disembarked.

The wounded were rapidly assisted or carried to the medicae, where Apothecary Dionys of the Fifth Company oversaw the patching up of their wounds. The Third had lost thirty-nine brothers at the fall of Sigma Fortulis, a bitter price to pay for any Space Marine company. Though none spoke a despairing word out loud, a silent but unmistakeable pall of sorrow hung over the fortified landing zone.

Cassius knelt by Brother Pythius, who lay stretched out on the ground. Pythius belonged to one of the Devastator units that had been stationed on the upper level of the fortress, and his leg armour was fitted with bracing plates to compensate for the weight of the lascannon he carried into battle.

Pythius’ breastplate, helmet and shoulder guards had been removed to show the massive acid burn that had dissolved a chunk of his chest. It was a hideous wound. Tyranid bio-acids were horrifically effective, and few who suffered such a direct hit survived. Pythius was of solid and strong stock even by Space Marine standards, a factor that made him worthy of carrying one of the Chapter’s heavy weapons. Even so, he was fading.

Cassius read the stricken warrior’s life signs from the panel on the forearm of his armour. Dionys had already ascertained that one of Pythius’ hearts and two of his lungs had been destroyed, and the advanced clotting agents of Space Marine blood had not been enough to prevent massive blood loss. Cassius lifted one of Pythius’ eyelids and saw the pupil remain wide and black, even in the glare of Kolovan’s merciless sun.

Somehow he still drew breath, but it was shallow and gurgling. Blood welled up in the yawning mouth of his wound with each inhalation. Pythius had been among the Ultramarines to storm the Basilica of Lord Phenoborra and slay the living blasphemy that nested inside. He had bested two Praetors of Ulixis in duels during the ten-yearly gathering of the Ultramarines’ successor Chapters.

He would not see a battlefield again.

Cassius let Pythius’ eye close. ‘We will see the end of sorrow and defeat,’ he said. ‘We will see the end of mourning for our lost. But we will not see the end of war, nor of our duty to fight it. Lesser men bemoan the terror of death, that we shall die with our duty undone. But we know that there shall be a final battle. The Emperor shall marshal all those for whom he has wept, and the Great Enemy shall be defeated at the end of all things. Stand beside the primarch and the Emperor, Brother Pythius, and never truly die.’

Pythius’ remaining lung quivered and sunk, and was not re-inflated. His mouth hung open, and in the ruination of his chest wound, his one heart stopped beating. His armour automatically dispensed stimulants to start it again, but Dionys had already ministered to Pythius and found no way to counteract the massive damage he had suffered.

At least they had recovered his body. Soon Dionys, who was currently tending to less catastrophic wounds, would extract Pythius’ gene-seed, and this battle-brother’s story would be over.

‘One more for us to avenge,’ said Captain Fabian. He had watched Cassius ministering to the dying Pythius in silence.

‘I will remember his death the next time I meet the enemy in battle,’ said the Chaplain.

‘We cannot all see our fallen brethren as fuel for the fire,’ said Fabian. ‘Most do not try to find ways to use their deaths. We just mourn them.’

‘I mourn them, too. I feel every death as you do,’ replied Cassius. ‘But I must make every death another reason for revenge, so each battle is a personal one.’

‘That must make it easy for you, when our lives are lost on your initiative.’

Cassius stood up and stepped away from Pythius’ corpse. Captain Fabian’s face had been dressed and the stump of his arm sealed with synth-flesh. His remaining eye stared at the Chaplain unblinkingly.

‘The Swarmlord had to die,’ Cassius said.

‘We had our orders,’ said Fabian. ‘You had my orders. On Macragge we all bow to your authority, but this is my company and my orders were to hold the fortress. Your veterans left their post, Lord Chaplain, and the lower levels were overwhelmed. We could have held on if you had been there to rally them. We could have broken the tyranids. Good men like Brother Pythius might still be alive.’

‘With the Swarmlord still in command of the xenos?’ replied Cassius. He did not raise his voice – he had not raised it in true anger against a fellow Ultramarine for many years. It was enough that he wore the colours of a Chaplain, and had the shattered face of one who had seen every form of war. ‘We robbed the hive mind of its most potent weapon, and we destroyed a foe whose death will inspire the whole Chapter for years to come.’

‘You think I care a damn for inspiration? We could have held the fortress, Cassius!’

‘You do not know that, captain.’

‘No, I do not. Because I never had the chance to find out. Now thirty of our brothers lie dead and Kolovan is no closer to deliverance! What does it matter how inspired we are if we cannot fight as one?’

‘Slaying the Swarmlord is the direst blow we could strike against the xenos,’ said Cassius, still keeping his voice level. ‘You know its history, what it is capable of.’

‘You did not fight to drive off the xenos!’ snapped Fabian. ‘You fought for yourself! Because you wanted revenge, and that meant more to you than your duty!’

‘If you wish to call me out, captain,’ said Cassius, ‘then Lord Macragge will hear you in the Chamber of Corrections. For now, you waste our time. The fighting is not done.’

Fabian’s body language suggested he was about to shout Cassius down, or even throw a punch. But the moment passed, and he said nothing.

‘When we have despatched the xenos and have returned to Macragge, Chapter Master Calgar will hear your protestations,’ said the Chaplain. ‘Until then, we must bury our differences. In unity we are strong. These are the words of the Codex Astartes.’

‘So they are,’ said Fabian. ‘But when the time is right, I will have words of my own.’

Fabian swallowed whatever more he had to say, and turned away to rejoin the brothers of his company, who were tending to their wargear. There was no time for extensive repairs. They would all bear the scars from Sigma Fortulis for some time yet.

‘Lord Chaplain,’ said Sergeant Verigar, who had waited for Fabian to leave before approaching. ‘There is news from the Adeptus Mechanicus.’ Perhaps he had heard the exchange, perhaps not. Cassius chastised himself for allowing that confrontation to happen in public.

‘I was informed,’ said Cassius. ‘What do the tech-priests of Ryza have to say?’

‘That’s just it,’ replied Verigar. The two missing fingers of his hand, blasted off by the flesh-eating bio-ammunition of a termagant, had been replaced by crude, claw-like bionics. It was basic work compared to the flesh replacements that could be fashioned in the apothecarions of Macragge, but it would allow him to hold a gun. ‘The magos wishes to speak with our commanders personally. He says that his research team has been working on potential biological counters to the xenos. Though he used quite a few more words than that when he described it to me.’

‘What do you think of this tech-priest, sergeant?’ asked Cassius.

‘It’s not my place to say,’ Verigar replied. The sergeant looked over the landing pad with its wounded Ultramarines. Some had lost limbs, some would not fight again on Kolovan. One or two might never fight again, in spite of the apothecarion’s expertise. Verigar sighed. ‘I just don’t have much time for Mechanicus double-speak today, Lord Chaplain. The Kraken has taken too many of us here.’

‘Then you will rejoice all the greater when they are cast into the void.’

‘I hope so. He’s waiting for you in the holomap chamber.’

Magos Uranios Rothe had installed himself with his servitor retinue in the chamber the strike force commanders had used to scrutinise the surface of Kolovan via the holographic projector. The servitors stood beside him holding the various implements of office – his staff, a datapad set in a panel of ornate hardwood, and a heavy cog-shaped medallion. The air in the chamber was hazy with the oily incense constantly exuded by Rothe’s mechanical body. Captain Galenus stood nearby, and gave Cassius a grim nod as he entered.

‘It is good to see you again, Lord Chaplain,’ he said. ‘You have earned great glory for our Chapter by killing that xenos monstrosity.’

‘Captain Galenus,’ Cassius said. ‘Fine work at the faultline. Now let us see what our guest has to say.’

The magos had not acknowledged Cassius as he walked in. The targeting lenses on the gun-servitors whirred as they focused on the newcomer.

‘So,’ said Cassius after a long moment of silence. ‘Finally the Adeptus Mechanicus takes an interest.’

‘You are the one called Cassius,’ said Rothe, finally acknowledging the Chaplain.

‘Lord Chaplain Ortan Cassius of the Ultramarines. Master of the Reclusiam. Defender of the Soul of Macragge.’

‘Low Gothic is too inefficient a language to convey the full complexity of my title. I am Magos Rothe, that will suffice.’

‘The magi of Ryza have focused their efforts on defending their own system,’ said Cassius. ‘I was led to believe Kolovan was outside their zone of interest. And yet you are here, and your coming here was not without risk. So I must ask why.’

Rothe’s mostly-human hand reached for the hem of his hood and drew it back. The face underneath it was a mask of ghostly-pale skin patched around metallic components. Rothe’s eyes were brass-rimmed silver orbs without pupils, linked by circuitry to the steel hemisphere that took up half his skull. His mouth was a lipless slash in his face, atrophied with inaction, for his voice was projected from a grille mounted over his larynx. The impression was that of a mummified corpse, resurrected and rebuilt with incongruous mechanical additions.

Both the magos and the Chaplain were, by any human standard, hideously ugly. For a moment Cassius saw his own face reflected in the sheen of Rothe’s bionics: the seared flesh, the pitiless mechanical eye. Each of them wore their mutilations with pride, though for very different reasons.

‘I fear I have yet to completely shed the manacles of the flesh,’ said Rothe. ‘One day the Omnissiah shall grant me freedom from the weakness of the body. But I have alterations enough for our purposes.’

‘And what are those purposes?’ Cassius was aware he was being short with the magos, but his dealings with the Adeptus Mechanicus had also taught him of their strange view of diplomacy. Among themselves they used infinitely complex honorifics and protocols of binary machine-speak, but with outsiders, they tended to lack the capacity for the normal interaction required to be basically respectful.

‘To cleanse the tyranids from Kolovan,’ said Rothe.

‘Ryza does not consider Kolovan a valid use of resources,’ said Cassius. ‘That much has been made clear from the responses to our communications with the tech-priests. If the Mechanicus intended to liberate this world, they would send me more than one magos.’

‘It is true that the planet itself is of no particular strategic value,’ said Rothe. ‘You have presumably come to the same conclusion. In any case, the civilian population is already dead. What is of great importance is the research that I have been conducting here.’

Cassius folded his arms. As good as he was at reading the body language and emotions of his battle-brothers, he could glean no information from Rothe’s expressionless face. ‘Tell me about this research.’

‘Our initial experiments involved the synthetic replication of an exogenic sequence, which was largely unsuccessful, and required a revised approach. For the second round of tests, we lined-’

‘Magos.’

‘Ah yes, my apologies,’ said Rothe. ‘Brevity. My research involved the design and refinement of various antiviral agents designed with the express purpose of altering the living tissue of biological life forms. Including xenoforms.’

‘“Altering?”’ said Cassius.

‘The initial thrust of our research was focused on the cure of various genetic maladies common amongst the Imperial population, but as we began to study xenos biology, we realised that our methods could be turned to a more aggressive purpose. One particular alien species studied was the Kraken strain of the tyranid genus.’

‘You say you have a biological agent we can use against the tyranids?’ asked Cassius.

‘It is still in the early stages of development,’ said Rothe. ‘It has not been field tested, and therefore I cannot claim empirically that it will work, but the theory is sound. It is an airborne antiviral designed to spread swiftly, and to invade and break down the organs of the target xenoform.’

Captain Galenus stepped forward quickly.

‘You have this agent with you?’ he asked.

‘No. The antiviral samples are all stored in secure holdings at xenopathology research base Zeta-Epsilon Twelve, located approximately one-point-seven-six kilometres beneath the city of Harienza,’ said Rothe. ‘The city has fallen. I have left a small retinue of bodyguards protecting the laboratory, but any attempt to extract my equipment would be futile. That is why I require assistance from the Adeptus Astartes.’

‘You’re saying this antiviral can infect the entire hive fleet?’ asked Galenus.

‘Indeed.’ Rothe may have smiled, but Cassius could not be sure. ‘Eventually. It will take several hours to spread through the atmosphere, but once an organism is infected, it will spread the pathogen to every creature it comes into contact with. The Kraken has placed itself in the path of the very weapon designed to kill it.’

The door opened and a swirl of ash soared into the chamber. Captain Fabian entered. He stepped to Galenus’ side, and clapped his fellow captain on the shoulder. His missing hand had not been replaced with a temporary augmetic yet, and instead rested in a sling at his side.

‘Throne, but it’s good to see you in one piece,’ said Galenus.

‘That, my friend, is a very poor choice of words,’ said Fabian. ‘So what does our honoured guest have to say for himself?’

The magos’ eyes blinked and whirred as he turned to Fabian, but Galenus cut him off before he could speak again.

‘Magos Rothe here claims to have access to a targeted biological weapon designed to destroy the tyranid xenoform,’ he said.

‘Truly?’ said Fabian. ‘Then why are we standing around?’

Cassius shook his head. This was all so predictable.

‘Do you know how many times I have heard scientists tell me that they know a fool proof way to defeat the tyranids?’ he said, turning to the magos. ‘How many deadly viruses have been unleashed that would finally eradicate the xenos threat once and for all? And do you know how many of these miracle weapons have been successful?’

‘My Lord Cassius,’ said Rothe, voice-grille hissing with irritation. ‘I assure you that my research indicates a success rate of ninety-eight point eight-three-five per cent. Dispersed into the atmosphere in the correct volume, this strain will begin to break down the internal organs of every tyranid on Kolovan.’

‘This is worth a shot, Chaplain,’ said Galenus.

‘There is only one way to purge the xenos,’ said Cassius. ‘With honest sweat and blood, and with faith in the God-Emperor. You seek an easy victory, and that is a path to indolence and corruption.’

‘No,’ said Galenus. ‘It is not. It is a way to contain this threat before it reaches the core worlds. I admire your zeal, Lord Chaplain, but I beg you to think of the repercussions if the hive fleet finishes gorging itself here and moves on to another world.’

‘We have no assurance that this will work, captain,’ Cassius protested.

‘It is a tactical opportunity that we cannot afford to ignore,’ said Fabian. ‘I too would rather fight the enemy face-to-face in honest battle, but our responsibility to the surrounding Imperial worlds demands that we attempt this.’

Cassius shook his head. ‘We can follow this lead, brothers,’ he said, ‘but I tell you that I have seen this tale play out a dozen times before. Kolovan will be liberated with the blade and with the bolter, not with this virus.’

‘Actually, Lord Chaplain, it’s an antiviral,’ said Rothe. ‘The difference is subtle, but…’ He trailed off as Cassius turned his ruined face towards him.

With the tyranids to the east cut off by the newly-born Transadverican Gulf and those further west in confusion with the fall of the Swarmlord, the Ultramarines’ foothold was secure enough to begin landing the strike force’s heavy armour. Two squadrons of Predator battle tanks, under Sergeants Dovan and Fenikos, were dropped in reinforced lander pods alongside Sergeant Boreas’ trio of Vindicator siege tanks. Ancient Tessarchus, the Dreadnought who had served as captain of the Third Company before falling in battle, was brought down alongside the tanks to serve as both mobile artillery and a spiritual mentor to the battle-brothers of the Third Company. Beside them rested Peryton Prime and Peryton Secundus, the pair of Stormtalon gunships fully configured for ground attack. The Peryton squadron had provided support to the Fifth Company’s battles for many years and the craft bore its black trim.

‘The vehicles are fuelled,’ said Techmarine Herodus as he and Cassius watched the rows of tanks being made ready for the coming operation. ‘The rites of supplication will take less than an hour. Then we can begin.’

‘Have their machine-spirits singing in unison, as those of the Dagger of Macragge did at the battle of the Black Saint’s Rift.’

Herodus nodded in agreement. ‘Truly, I was inspired by the echoes of Mars that day. I shall pray as I did then, Lord Chaplain. The steel tide shall wash the xenos from this world.’

There was something of the zealot about Herodus. He had brought back with him from the traditional Techmarine’s pilgrimage to Mars a devotion to the machine-spirits of the Chapter’s vehicles and wargear. He functioned much as a Chaplain did, but to the insubstantial, obscure machine-spirits of the ancient cogitators in each tank and spacecraft. Cassius watched Herodus walk between the parked tanks with a vial of sacred machine-oil in one hand and a data-slate in the other. It did not take much to spur him on to redoubling his efforts in having the strike force’s big guns fire more efficiently than the crews alone could manage.

‘The ministrations are complete,’ voxed Herodus eventually. ‘The spirits are eager to feel their engines roar!’

‘Company, embark!’ ordered Galenus over the vox.

‘Third Company, to your transports!’ echoed Captain Fabian. The Ultramarines were already climbing into their vehicles as the engines turned over and the rapid throb of the gunships’ rotors rose in pitch.

‘Emperor’s own fortune be with you, Chaplain,’ said Galenus as he left to join his company.

Cassius reached his Rhino as the gunships were lifting off, soaring into the air on columns of exhaust flame. Two forces roared away from the landing zone. The larger, under Galenus and Fabian, was accompanied by the Predators and Vindicators, for they were expected to face the bulk of the resistance from the tyranid organisms already infesting the jungles to the north. They would be the armoured spear that would strike into Harienza, securing a beachhead for Cassius’ smaller force to make their way into Base Zeta-Epsilon Twelve and secure Rothe’s research. A cloud of dust was churned up from the rocky desert as the force advanced, the transports flanked by the tanks, with the gunships casting their rippling shadows across the ground ahead.

‘Brothers, think on your prayers and of our fallen!’ voxed Captain Fabian to the whole force. ‘Crush the xenos beneath our tracks! Break them against our guns! We have spent too much blood on this world. This is the deathblow, my friends. This is how it ends!’

Cassius had not spoken with Fabian since their altercation after the return from Sigma Fortulis. He had no need to explain himself further – he was the Lord Chaplain of the Ultramarines, and he was beholden to none save Chapter Master Marneus Calgar. And in any case, he had made the right choice. The Swarmlord had to die. It had overseen the destruction of the whole First Company during the Battle for Macragge, and it had almost slain Lord Calgar himself. The beast had fallen only at immense cost. If it had been left to mastermind the infestation of Kolovan this world would be lost.

Battle-brothers had fallen. Cassius would mourn them. But he had made the right choice, he was sure.

Cassius opened the commander’s hatch and put his head up to get a clear view of his surroundings. The two prongs of the strike force were making rapid time, the experienced drivers riding the Rhinos and armoured vehicles over the rises and falls in the broken ground. On the horizon to the north was a dark band of trees where the desert gave way to the humid forests fed by the hot springs and underground rivers of the region. Cassius could just make out the spires of Harienza reaching up to the level of the spore clouds gathering over the forest. This was his force’s destination, an administrative and cultural capital nestling among the folds of the rainforest. There had been no contact from the city since the Ultramarines landed, and according to Rothe its mortal defenders had quickly broken and scattered under the tyranid advance. Enemy resistance was expected. Survivors were not.

The Rhinos entered the treeline, and came onto the main arterial highway leading from Harienza. It was a wide, double-laned route, designed for the big cargo haulers that would normally be lugging ore and lumber to and fro between the coastal cities. Now it was choked with hundreds upon hundreds of abandoned vehicles, stretching before the Space Marine convoy as far as they could see. Some were gutted and burned, but most were parked gently in the line, doors open or windows smashed.

‘They tried to flee when the spores began to fall,’ said Remas over the vox. He was travelling in the lead Rhino with Magos Rothe and two of his gaunt, copper-bodied valet servitors. Cassius caught a glimpse of his black and yellow armour as the Rhinos rumbled around an upturned two-storey conveyor, lying in a field of shattered glass. ‘Futile. There was nowhere to hide from the xenos.’

‘No sign of any survivors,’ voxed Sergeant Tevian. ‘And no bodies at all. I can’t even see any blood.’

‘The tyranids do not leave corpses,’ said Cassius. ‘They consume it all, every scrap of biological matter.’

The Ultramarines’ convoy peeled wide again, leaving the rockcrete surface of the road as they swerved around a jack-knifed lumber hauler, oil still dripping from a rent in its engine. As they passed that obstruction, they saw the first of the roadside camps. They had sprung up behind the string of charred vehicles, makeshift shanties clustered around the towering trees, competing for the sliver of sunlight that fell where the road had been cut through the jungle. The humans had attempted to set up a perimeter. There were crude barricades of corrugated iron, and Cassius saw several mounted stubguns, now abandoned like everything else, shell casings and drum barrels lying scattered around them.

‘They fought,’ said Tevian. ‘Until the end.’

The Chaplain could picture the mortals’ last moments, those who still carried weapons firing wildly into the depths of the forest as the enemy struck the convoy in force, dragging away friends and family. Nowhere to run. Nothing to do but fire until their pitiful weapons ran dry, and wait for the tide of horrors to engulf them.

‘We are too late to help the people of Kolovan,’ Cassius voxed on the open channel. ‘They are lost. This planet is dead. Yet its death need not be in vain. Here the tyranid will burn in the fires of our hatred, and a hundred loyal Imperial worlds will be spared the horror of its degradations.’

They passed a small, humble two-seater, crumpled between two heavy goods vehicles. The passenger side door was open, and glass and shattered metal had spilled onto the road surface. Amongst the debris was a tiny metal model of a Warhound Titan, a child’s toy rendered with crude but charming detail.

‘That will be the legacy of Kolovan,’ said Cassius, ‘and we will not forget it.’

The ghost convoy stretched on. As the spires of Harienza loomed ever closer, Cassius began to hear the echoing report of cannon fire. The leading tank squadrons had engaged the enemy.

Chapter Six

The armoured strike force of the combined Third and Fifth Companies had made good time from the landing zone over the western desert towards Harienza. Towards the coast the land was flat and sun-baked, the perfect terrain for tracked vehicles. They entered the forested scrubland that surrounded the city while the sun was up, though thanks to the ever-increasing spore clouds and the aftermath of the Transadverican eruption, the light was dull and hazy.

Finally, the column came to the southern gates of the city, which hung shattered and broken, no longer blocking access from the highway. The tanks and armoured vehicles advanced at pace, while the gunships circled above, watching for the first signs of alien activity. It did not take long. Roused by the terrific noise of roaring engines, the tyranids bled through the shattered hab-blocks and complexes of the southern city, and streamed towards the Ultramarines.

With their heavy armour in the field, the Ultramarines abandoned the defensive doctrines of the Codex Astartes, and instead embraced its concise, ruthless approach to the overwhelming assault.

Predator tanks crashed through barriers and over mounds of fallen rubble, blasting away with heavy autocannons and bolters at clusters of the enemy, which surged from the mouths of hab-blocks and the caverns of torn-open sewer outlets. These tanks were light infantry killers, armed not with lascannons for tank-to-tank warfare, but with weapons designed to tear through the enemy infantry, softening them up for the steady advance of the Ultramarines Tactical squads. The front ranks of the swarm simply came apart under that sustained barrage, but there was no time to hold a defensive position and thin their numbers. The Third and Fifth needed to push further into the city at speed to secure the grand plaza, a defensible position located near to research complex Zeta-Epsilon Twelve.

Fortunately the Scout units, advancing ahead of the main force the previous night, had done their job well. Ghosting into the city in the early hours of the morning, they had designated key fire zones, laid down targeting beacons and identified the areas with the highest concentration of enemy movement.

Armed with this vital data, the armoured task force went to work.

Annihilator tanks and the cumbersome Vindicator siege variants joined the gun-line. The former fired searing blasts at structural weak points in the targeted buildings. These deadly pulses of scarlet energy were followed by the sound of a planet tearing in half, as the heavy Demolisher cannons mounted on the Vindicators hurled forth shells of hideous explosive power that entirely obliterated the lower levels of each structure, collapsing thousands of tonnes of dense rockcrete to crush and seal the enemy within. Great plumes of dust and smoke swirled above the devastation, winding around the pillars and pathways of the upper habitations.

In the wake of this catastrophe came the Ultramarines Tactical squads and Devastator units, marching steadily across the broken rubble, bolters blazing. Thousands of the hated xenos were obliterated before the Space Marines even came under sustained enemy fire. The push was relentless.

Harienza was a cramped and cluttered city. Tall smokestacks rose from the central core, built around a roughly pyramidal conglomeration of manufactoria and hab-blocks. The docks reached out with fingers of rockcrete to receive the ships that had brought ore to the refinery furnaces. Harienza’s principal purpose had been, like the rest of Kolovan, to feed the industrial hunger of Ryza with the products of the planet’s unusual geology.

That time was over now, and only devastation remained. The stains of the city’s trauma were visible even from a distance, as the Ultramarines approached through the colossal gate leading to the administrative and political districts. The carcasses of ruptured transport vehicles were piled in smoking clusters. Fires burned everywhere, adding plumes of dirty smoke to the discharge from the smokestacks. Huge banners of stitched sheets hung as distress markers, to summon aircraft that had never arrived. The handful of spaceport pads dotted around the city’s uppermost surfaces were circled with fire and wreckage, left behind as the people had gathered there in a desperate attempt to find a departing craft.

Following in the wake of the Third and Fifth’s armoured units, the transports passed through the threshold of a huge gate, a soaring arch decorated with the gilded figures of robed tech-priests, and into Harienza proper. Though several layers of the city were built above this lower stratum, the roads here were wide and the buildings tall. They housed the mechanisms of finance and government, presenting a handsome, marble-fronted face to new visitors.

The avenue continued through columned civic buildings and monumental statues of Kolovan’s historical heroes. It opened into a wide plaza which had once boasted a magnificent garden, now cratered and burned by artillery fire. On all sides the buildings loomed, windows shattered and faces marked with great holes where heavy ordnance had landed. Lines of sandbags and portable cover had been left abandoned on the roadways, along with the smouldering metal carcasses of light-armoured vehicles.

‘There was a major engagement here,’ said Sergeant Remas over the vox. He and his five remaining battle-capable veterans were following in the armoured vehicle behind Cassius. ‘Perhaps the last stand of the local Kolovan militia.’

It certainly looked that way. The grand forum, far more elaborate than the rest of the city, would once have been a symbol of Harienza’s proud history. It was not surprising that the city’s mortal defenders had defended it so fiercely.

‘They met their end well,’ said Cassius. ‘Now, our duty is to avenge them.’

The column halted near the entrance to the plaza, just before the ruined garden park. Storm bolters swivelled to cover the buildings on either side, and Tactical squads began to filter out of their transports.

‘Lord Chaplain,’ voxed Captain Galenus. ‘We are in an entrenched position one block north of the plaza. The ground is relatively open here, which means the tanks have room to move. I’ve sent two Annihilators back your way, just in case something slips through.’

‘Confirmed,’ said Cassius. ‘Be ready to cover our retreat once we have retrieved the objective. We cannot become mired in a pitched battle here. This must be a swift extraction.’

‘Understood. Courage and honour, brother.’

‘Courage and honour,’ Cassius replied.

The access doors on the Rhino ground open, and the Chaplain and his squad rushed out, weapons raised and ready. Rothe clambered out behind them. His eyes darted to and fro, and he flinched as an explosion to their left sent a great swathe of flame and smoke skyward.

‘Magos,’ said Cassius. ‘We will keep you alive. Lead the way.’

‘Contact at ninety degrees!’ came a vox from the other side of the convoy. Other Ultramarines squads were deploying from their own Rhinos, and Cassius heard the first volleys of bolter fire rippling out as the enemy poured through the wreckage of the administratum quarter and into the open ground of the forum.

The xenos leapt from windows and scrambled free from holes torn in the earth, and were met with bolter fire and blades. Alongside the volleys of the tactical squads, the storm bolters mounted on each vehicle opened up, a torrent of mass-reactive rounds that churned the earth, shattered walls and tore hormagaunts and termagants to shreds. Larger creatures began to push in on the Ultramarines position, smashing their way through half-destroyed buildings in order to get at their prey. They were met by heavy weapons fire, flashes of plasma and the smoking contrails of missiles. A huge siege organism barrelled into their line from the left, tipping one of the vehicles over and tearing out its underbelly with wicked talons. It roared and turned to do the same to the next vehicle in the line, but as it did so a searing beam of energy speared forth from behind the Ultramarines position. It ripped a smoking hole through the creature’s mouth, spraying the contents of its head out of the back of its skull. An Annihilator rolled forwards, lascannon still red-hot from the heat of the blast.

There was an earth-shaking rumble from the destroyed garden as a great torrent of soil and ash was displaced, torn open by a massive wormlike creature that screeched as it emerged into the light. Its front limbs were enormous scything talons and its mouth yawned open, splitting vertically to reveal a glistening gullet lined with spiny teeth. The creature was enormous, and as it erupted from the ground its full height surpassed that of the other siege-beasts by several metres. It crashed down next to the Annihilator tank, armour plates along the creature’s back shifting as it brought those colossal talons up for a killing strike.

The Annihilator’s lascannon flared with power and fired another bolt of scintillating energy, which flashed towards the creature. The tyranid moved with snakelike speed, looping out of the way as the shot fizzed past it and vaporised a marble plinth, sending stones flying through the air. The serpent-form reared up again, raised one of its enormous claws, and brought it down like a guillotine across the upper hull of the Annihilator.

The blade carved right through the tank. The tyranid screamed as it split the vehicle down the middle, revealing its mechanical innards. The Space Marine gunner slid from the exposed carriage, bloody and torn. The creature lifted a limb and sent one torn half of the Annihilator sailing through the air to crash into a Rhino, which crumpled under the weight. Despite his horrific wounds, the stricken Ultramarine drew a bolt pistol and fired up at the monster that towered over him, dragging himself away from the wreckage and leaving a bloody trail with his two shattered legs. The tyranid flipped him into the air with its free claw and caught him in its mouth as he fell. There was a sickening crunch of broken ceramite.

‘It’s a trygon,’ said Remas, as the veterans took cover among the columns. ‘They came through the foundations on Sotha. They brought the siege-beasts into our fortress-monastery. They dig the tunnels and the others follow.’

Out of the rent the trygon had torn in the earth, smaller creatures emerged. These were not the lesser tyranids based on the termagant genus that teemed elsewhere on Kolovan – these were larger and moved not on their six limbs, but floated ponderously above the ground with the aid of wheezing, gas-filled dorsal bladders. Four of their limbs ended in whip-like tentacles tipped with dagger-like talons. Their faces were fringed with tendrils that dripped transparent slime.

‘We must make for Saint Juno’s Way,’ said Rothe. The tech-priest clutched his fine hardwood data-slate in front of him like a shield, peering over it and flinching at the screams and roars of the alien. ‘We can pass through the Hall of Records, there.’

He pointed a skeletal, metal finger at the building to their right, a once-impressive domed hall now scarred by explosions and dusted with ash. To reach it they would have to cross open ground.

‘Sergeant Verigar,’ said Cassius, hefting Infernus and placing one hand securely on the magos’ shoulder. ‘Your squad is with me. Everyone else, hold this position.’

The Chaplain and his men left the cover of the column, rushing forth across the open street towards the marble steps that led to the Hall of Records. Biological ammunition hissed and burst at their feet as they ran, but Cassius used his bulk to shield the terrified Rothe, who was issuing some sort of high-pitched static squeal as he tried to keep up with the Space Marines. Brother Martos made the stairs first, advancing in a textbook room-clearing stance with his bolter jammed into his shoulder. As he entered through the gilded doors, which were smashed almost entirely off their hinges, he swept to the left, followed by three more of Verigar’s squad. Cassius heard the roar of his bolter, and an alien shriek was cut off abruptly. Holding the magos firmly at his side, Cassius went right. Two forms rushed at him, and he put a torrent of bolt shells through them. One tried to scrabble towards him on one mangled leg, and he crushed its skull with his crozius.

The hall was a place of old, age-polished wood, the ceiling two storeys above decorated with eagles in tarnished gilt, with broken glowglobes hanging like a map of the stars. Millions of forms, parchments and datacards lay scattered on the floor, and fire had reduced much of the interior to a lattice of charred matter. Several more hormagaunts burst from the shadows, and Sergeant Verigar’s men met them with a hail of fire and a flurry of bladework.

‘How far are we from the target?’ asked Cassius.

‘Two kilometres, across the city,’ said Rothe. ‘The Office of Application. The entrance is on the bottom floor, behind a secure door.’

‘Can you keep up?’

‘I must, Lord Chaplain,’ the magos said. ‘Only I have the ability to bypass our security procedures.’

It was an unfortunate necessity of the current operation that the Ultramarines could not maintain the breathless pace of their assault, which Captain Galenus believed would surely have destroyed the opposition in Harienza before it could regroup and counter-attack. Though he understood that they could not risk pushing too far forward and leaving Cassius’ group exposed, it felt to Galenus like leaving a job half finished, and he did not like that feeling at all.

‘Already they recover,’ Galenus said to Captain Fabian over the vox. ‘I do not like how exposed we are here, brother. The xenos could emerge from any angle.’

‘Pull the infantry in close,’ said Fabian. ‘We have encircled the forum and cleared the way for the Lord Chaplain. He’s not a man to tarry when a task needs doing. We’ll be out of here soon.’

Ahead of Galenus’ command vehicle the Predator tanks continued to scour the rubble of Harienza. Devastator squads had taken position in a ruined hab-block to the left of the armoured force, with a clear line of fire across the rubble wastes created by the siege tanks. The tanks were arranged in a wide semi-circle around the forum, with infantry support ranged ahead to forewarn of any mass deployment of anti-armour organisms. Thus far, such sightings had been rare, which reassured Galenus. The tyranids had yet to establish their repulsive bio-organic feeding structures in this city, and therefore they did not appear to occupy Harienza in significant force, at least compared to the numberless swarms that had overrun the western continents.

That said, there was no such thing as a small tyranid host. Already the aliens’ bizarre, hateful hive consciousness would be rushing fresh organisms towards the Ultramarines’ position.

‘Contact!’ came the vox-call from Vigilant Gamma. ‘We have siege-forms incoming, dozens of them.’

The rubble of the destroyed hab-blocks exploded once more. Galenus saw a flurry of spiked limbs, something vast bursting through the wreckage, displacing stones as big as houses. A wave of dust and ash billowed out, and through it came the tyranids. Waves of screeching hormagaunts hurtled towards the Ultramarines, and were met with volley fire from the Tactical squads. Storming forward in their wake came the siege-beasts, smashing through walls and hurling debris aside in their desperation to get at the front ranks of the armoured formation.

Predators and Annihilators opened fire in return, and the sky lit up with the scarlet flare of laser fire and the rippling muzzle flashes of the tanks’ autocannons. The broken ground in front of the Ultramarines’ position became a firestorm, so thick with flames, smoke and debris that Galenus lost sight of the enemy for a moment. Then the first pale forms began to break through the inferno, and he took hold of the Rhino’s pintle-mounted storm bolter and brought it to bear. It kicked satisfyingly in his hands as he aimed at a group of blade-limbed warrior-forms scrabbling out from underneath a fallen archway. The aliens came apart in a burst of ichor.

A flare of sickly green light screamed overhead, and Galenus ducked instinctively. The front of the vehicle behind his own erupted in flames, flipping up and over and coming to rest in a smoking heap.

There was a bellow to his right, and he saw a siege-beast with a tumorous growth on its left forelimb barrel through a squad of Ultramarines, sending them flying as it slammed into the Rhino they had been stationed beside, throwing the vehicle across the ground with a screech and a burst of sparks. Two of the Space Marines stayed down, but the others dragged themselves to their feet and began raking the back of the creature with bolt shells. One brother stepped forward with a flamer, and bathed the siege-beast’s lower torso in flaming promethium. Galenus swivelled his storm bolter and added his own shells to the barrage, but the siege-beast still refused to go down. Throne, they were tough.

‘Command squad, dismount,’ he shouted, and dropped from the firing point. His boots hit the steel floor of the Rhino, and he heard the clunk of the side access ports lowering. ‘Courage and honour, brothers! We fight for Kolovan’s lost souls, and for blessed Macragge!’

He drew his blade and a combi-melta that he had requisitioned from the armoury, not for the first time cursing the loss of his storm shield. The ramp hit the dirt, and Galenus and his men thundered out into the haze of battle.

After an hour or so of cautious advancement through the city streets, Cassius’ strike team reached Saint Juno’s Way, a narrow thoroughfare enclosed by the foundations of habitation towers that stretched hundreds of metres to the levels above. This part of the city was far removed from the pomp and grandeur of the forum. Instead it had the utilitarian look of an office district, a place where the endless, labyrinthine administrations of a working, trading city were processed. It had not remained untouched by the invasion. The streets had been churned up by extensive artillery fire and the road was a tangled mess of shattered, smoking vehicles.

‘There – the Office of Application,’ said Rothe, pointing to the remnants of a nondescript two-storey structure that was propped up in the shadow of a looming hab-block.

Like most of the workplaces that lined the street, the building had taken horrific damage. The entire right half of the structure had collapsed, leaving spars and pillars of rockcrete jutting out into the empty air like a shattered ribcage. As the team moved carefully through the scene of devastation, they could hear the thunder of cannon in the distance, louder and more frequent than before. It did not relent.

‘The Third and Fifth have engaged the main enemy force,’ said Cassius. ‘We must hurry.’

‘Follow me,’ said Rothe, rushing up the shattered steps.

They entered the standing half of the structure, which creaked and groaned around them. Inside it was a functional, wood-floored building, with a line of brass-grilled counters at the rear, behind which were stacked shelves upon shelves of documentation and a row of shattered cogitators.

‘This doesn’t look much like a research complex,’ said Brother Corrus.

‘Which is entirely the point,’ said Rothe. ‘This place processed applications for manufactorum equipment and construction gear. We of the Adeptus Mechanicus prefer to do our holy work in isolation, when possible. Our experiments here were sensitive, and interference from the planetary government would simply have obstructed the process.’

‘You mean to say they would not have welcomed a biological weapons facility underneath one of their cities?’ replied Corrus. ‘You surprise me.’

‘It is very short-sighted, is it not?’ said the magos. ‘You understand why we preferred to bypass any potential conflict.’

He led them to the counter, extended a mechadendrite with a flat, circular end, and connected it to a terminal on the wall. The brass grille swung open, and Rothe headed through a door in the back of the room. The chamber beyond was a storage room, with rows of filing cabinets filled to the brim with paperwork. Several had been knocked down, and their contents spilled across the floor. Broken strip-lights and wiring looped from the ceiling, still flickering in the gloom. In one corner of the room was a heavy, metal set of doors, with another panel at the side. Once again, Rothe activated the panel, his augmetics whirring softly as he bypassed whatever security measures kept the research base secured. Beyond, a set of stairs wound down into the darkness.

Rothe led them down, extending another tendril from within his robes that bathed the walls in a soft blue light. The emanation revealed a diagonally aligned shaft that reached to the low ceiling above, and a large rectangular platform with a low guard-rail.

‘This will lead us down to the complex,’ said Rothe, sealing the access door behind them as the strike team filed onto the lift. The magos pressed the palm of his organic hand against a panel set in the wall, and Cassius heard the soft, low hum of the magnetic field firing as the elevator began to descend.

‘How big is the complex?’ said Cassius. ‘How long will it take us to reach the objective?’

‘There are fifty-seven floors, each housing several laboratories and research stations,’ said the magos. ‘Pathogen sample storage is on the twelfth floor.’

It took several minutes for the elevator to reach its destination, but finally the massive lift-shaft doors groaned open. They emerged into a circular corridor, strobed by yellow hazard lights embedded in the ceiling every hundred metres. Pools of coolant and other liquids had seeped onto the rockcrete floor, and though the Space Marines could hardly feel it through their insulating warplate, armour diagnostics suggested the temperature down here was several degrees below what could have been expected. No one had come to meet the lift as it descended.

Rothe began to sputter in binaric. When Cassius turned to him, the magos held up a pale, thin finger. The Chaplain waited.

‘No one is responding on the private vox-link,’ said Rothe, after almost a minute. ‘Where is everyone? The orderlies? Magos Klaupt? Anyone? I don’t understand, why is the backup generator running?’

‘That is unusual?’ said Cassius.

‘We had enough reserve power to operate at maximum efficiency for several more months,’ said Rothe. ‘I told the staff to meet me here the moment I re-entered the complex.’

‘Perhaps the battle above knocked out a power source?’ said Verigar.

‘No,’ replied Rothe. ‘We are self-sufficient. This base is designed to operate outside the city grid.’

There was a distant, crashing thud that echoed through the corridor, and the shrieking hiss of something that could have been mechanical. Rothe visibly stiffened.

‘Weapons ready,’ said Cassius. ‘Magos, which way from here?’

‘To… to the left,’ Rothe stammered. ‘There is a stairway. Second door on the right.’

The facility beyond the main chamber was split into laboratories, each specialised in a different form of xenobiological research. The first was full of workstations, each with a brass-cased microscope and cogitator console, with doctrines of mental purity and thoroughness of thought carved into the rockcrete and steel walls. Rows of specimen cabinets and racks of test tubes ran off in one direction, with humming generators and tangles of power cabling in the other.

They found the first body propped up against a bulkhead on the second floor. It was a servitor-orderly, stocky and thick-limbed, with a grilled metal visor where a normal person’s eyes would be. Apothecary Soemnus examined the corpse. Something incredibly sharp had sheared through its spine, and finger-deep stab wounds marked its chest.

‘A quick, clean kill,’ said Soemnus. ‘Almost surgical. It detached the spine and struck at the heart and lungs. Any of these strikes would have killed a mortal outright.’

‘My staff,’ hissed Rothe. ‘My colleagues. They are in extreme danger. We must secure them, Lord Chaplain.’

‘Magos,’ said Cassius, resting one hand firmly on the man’s shoulder. ‘Gather yourself. We will find your fellow scientists.’

The Chaplain gestured for the strike team to continue. They passed cryo-chambers packed with strange organic samples in various states of decomposition. Mist clouded each chamber and Cassius saw warning runes flickering across holographic displays. Rothe gave a little binaric blurt of what the Chaplain assumed was distress as he passed each display. If there was one thing a magos despised, it was the loss of valuable data.

Past the test chambers they found more of the base staff. A severed hand clutched at the handle to a decontamination shower room. Blood pooled on the floor, dripping from a vent in the ceiling.

There was a faint, sharp sound in the distance. A sound like smashed glass crunching underfoot. The strike team raised their guns.

‘We are being tracked,’ said Regulus.

‘Be vigilant, brothers,’ said Cassius. ‘But be swift. Sergeant Corrus, Brother Kyvian, take point.’

They advanced at pace, clattering down stairwells and rushing through abandoned compartments and test chambers, Rothe leading them on whenever they came to one of the labyrinthine facility’s many junctions.

‘Here,’ said Rothe, pointing to a set of double doors that rested ajar at the end of a long, wide hallway, with corridors leading off left and right at equidistant intervals. ‘The access lift is here.’

Even Cassius, used to the harsh cold of Macragge’s polar mountains, could feel the chill here. Vapour rose from Rothe’s vox-grille, and as the Chaplain watched him, his normally expressionless face twitched just for a fraction of a second, his diodes flaring.

Brother Corrus ran ahead, sweeping his bolter left and right as he checked the first of the branching corridors. He ran to the second and did the same.

‘Clear,’ he shouted, turning back to the strike team. ‘Quickly, broth–’

Corrus’ body was lifted up and to the left as something heavy slammed into him. Cassius saw a shimmer of movement, as if a curtain of clear water had been poured momentarily across the hallway, and a spray of crimson burst from Corrus’ back. The Ultramarine fell, crashing across the steel floor with a screech of ceramite. The strike team opened fire, and Rothe gave a static squeal as the hallway disintegrated in a shower of plaster and rockcrete.

‘Cease!’ roared Cassius, and the bolters stopped firing. There was silence, except for the soft patter of falling debris.

Soemnus moved forward, bolt pistol raised and narthecium ready. He bent over Corrus and scanned his prone form with a scanner built in to the wrist-mounted device. After a moment he glanced back and shook his head.

‘Lictor,’ said Remas. ‘Assassin-form.’

Every member of the veteran squad had faced a lictor at one point or another. They were scouts and hunters, isolated killers whose presence, or rather the trail of bodies they left behind, often precipitated a full tyranid swarm.

‘That is what slaughtered my staff?’ said Rothe. ‘It has set back my research at least a decade. You must exterminate it before it does any more damage to my equipment.’

‘There must have been a breach,’ said Verigar, pointedly ignoring the magos. ‘Opened up in the fighting. That thing entered, and it’s been killing its way through here ever since.’

‘Stay close,’ said Cassius, ‘and watch the shadows. The xenos will strike again.’

The strike team moved forward, Apothecary Soemnus joining them with Corrus’ gene-seed secured. They pried open the heavy double doors and entered a circular elevator. It was only large enough for four Space Marines to stand abreast, so Sergeant Verigar assigned the rest of his squad to guard the hallway, while he, Kyvian, Soemnus and the Lord Chaplain descended.

‘The housing chamber is security level extremis,’ said Rothe, fumbling with his data-slate as the lift hurtled into the depths of the complex with stomach-jolting speed. ‘I am certain that the organism roaming this complex could not have penetrated its walls.’

‘That is what you told us about the upper levels,’ said Cassius.

They entered a short corridor dimly lit by pale, flickering lumen. After a dozen metres the hall ended in a thick ferrocrete door secured with three great bolts fashioned in the shape of cogs. Through an armourglass viewport at the top of the door, they could see the housing chamber. A huge spherical cavity was dominated by an enormous arm of brass and steel mounted on a central power unit. The deck overlooking the centrifuge supported several bulky cogitators with clacking valve towers and banks of whirring clockwork.

‘Get this door open, magos,’ said Cassius.

Brother Regulus, commanding the remainder of Verigar’s squad in the Sergeant’s absence, had arrayed his brothers in a standard, Codex-compliant defensive formation: overlapping fields of fire from both flanks, Brother Haldus’ flamer to the fore, ready to be brought to bear the instant the enemy showed itself. And now they waited.

‘You think the magos’ virus will work?’ said Haldus.

‘I think if it was that easy to be rid of the tyranids, we’d have done so long before now,’ said Regulus. ‘Perhaps it will give us an edge against them. Perhaps that’s enough.’

‘The Lord Chaplain’s not happy about it, I can tell,’ said Teriach.

‘He’s rarely happy, except when he’s knee-deep in enemy dead,’ said Haldus. ‘He wants an honest battle, and I’m of a mind to agree with him.’

‘Enough talk,’ said Regulus. ‘Concentrate.’

For an advanced research facility, Zeta-Epsilon Twelve was hardly quiet. The walls creaked and groaned constantly, and there was an ever-present electronic hum that set Regulus’ teeth on edge. Coolant dripped from the ceiling, and from the gaping holes that the Ultramarines’ bolt shells had torn into the rockcrete walls. Every now and then a heavy, mechanical clunk echoed through the hallway. Plenty of sounds to mask the enemy’s approach – as if the fact it could disappear entirely wasn’t enough already.

‘Tevian, auspex reading,’ Regulus said, and his fellow Ultramarine stowed his weapon and retrieved the handheld scanner from his belt. He raised it and thumbed the activation switch, slowly moving the device from side to side in front of him.

‘Something’s playing merry hell with the readings, brother, but the hallway looks clear,’ said Tevian.

There was a crash from the closest door on the right, and a beam of yellow light rolled back and forth across the hallway in front of the Ultramarines, before coming to a halt.

Tevian glanced back at Regulus, who gestured forward. Tevian stood, and inched towards the branching corridor. ‘Cover me,’ he said.

Brother Morvion went to Tevian’s side, bolter ready as his fellow warrior took another reading.

‘Clear,’ said Tevian. ‘Just a broken hazard light.’

The ceiling above Brother Haldus exploded, steel plates raining to the floor as a shadow wrapped around the Ultramarine, lifting him easily from the floor. Haldus’ flamer went off, and a tongue of flame licked the panelled walls, melting plasteel and forcing Regulus to throw himself to the floor. He felt the wicked heat as the flames roared over his head, and rolled to one side, bolter aimed. There was a series of sickening crunches, and he heard Haldus groan in pain. Then the Space Marine was launched towards the oncoming Tevian and Morvion, leaking dark blood.

No, not blood.

‘Get down!’ Regulus screamed, but it was too late. Haldus’ punctured promethium tank detonated with a blast that shook the walls, erupting in a colossal inflagration that sent a tide of fire rolling out across the roof of the chamber. The shock wave slammed Regulus into the far wall, where he hit hard enough to dent ceramite. Dazed, swaying, he hauled himself to his feet, in time to see the shadow slide between the doors leading to the elevator shaft. He caught a glimpse of pale, writhing tentacles, and ancient, pitiless eyes filled with hungry malice. He fired, staggered to the brink of the shaft and fired again, tracking the faint shimmer of movement as it crawled and leapt from side to side, so fast it seemed little more than a blur. Then it was gone, vanished into the depths of the chasm.

‘Sergeant Verigar,’ Regulus voxed, and his voice seemed tinny and distant. ‘You have incoming. The xenos has broken through, it’s closing on your position.’

Cassius entered the housing chamber, crozius and combi-weapon raised. He stepped over a carpet of dead servitors and lab staff, each corpse covered with a patina of frost. It was deathly cold in here.

Soemnus checked the bodies.

‘No entry wounds,’ he said. ‘They froze to death.’

‘It was important to keep the samples at below zero,’ said Rothe. ‘There is a temperature regulation system on the thirty-second floor. It must have malfunctioned.’

‘No,’ said Cassius. ‘It was sabotaged. The creature could not breach this chamber, and so it found another way to kill those who had sought safety here.’

‘How would it know to do that?’ said Verigar.

‘The creature we saw is a scouting and assassination form, intelligent and dangerous,’ said Cassius. ‘It is theorised that these creatures can absorb the memories of devoured prey.’

The magos knelt by a short, orange-robed figure that was huddled against one of the cogitator devices. Its pale arms were wrapped around its shoulders in a futile attempt to stay warm. Clawing fingers had turned blue and purple from cyanosis.

‘Magos Hypatioth,’ said Rothe. ‘His work on viable methods of endotoxin conversion was weak and filled with obvious fallacies. But he provided a welcome sounding board for my more complex theories. It will take many years to replace him.’

Rothe stood, and moved towards the control suite overlooking the centrifuge.

‘This will take me a few moments, Lord Chaplain.’

‘It’s broken through,’ said Verigar suddenly, activating his chainsword with a grinding roar. ‘It’s heading towards us.’

Kyvian rushed to the door control, and raised a hand to the control mechanism. The doors began to slide shut, and Kyvian turned to take position guarding the sealed entrance. As he turned there was a clattering rush, and he was pitched forwards, sliding slightly on the frost-slick floor. Cassius saw the light above his fallen brother coalesce into a monstrous, bone-spurred form, two giant, jagged claws raised to skewer the Ultramarine through the back. Twin pools of obsidian stared at the Chaplain from beneath the ridged carapace of its skull, and its mouthful of feeder tendrils writhed hatefully as it gazed at him.

He answered that gaze with Infernus. The combi-weapon spat its hate at the monstrosity, and mass-reactive shells crunched into its spiked exoskeleton. There was a pained screech and suddenly it was gone, a shapeless blur that swept behind the row of cogitators to their right. Verigar tossed a grenade, and Kyvian rolled to the side, leaving a trail of blood across the floor from a wound on his back. The grenade went off, and two cogitators exploded in a shower of sparks and torn metal.

Silence fell, aside from the faint whir and click of the magos interfacing with the command console. Kyvian got to his feet, growling in pain, and leaned against a display console. Verigar spread out to the right, while Cassius and Apothecary Soemnus kept to the centre of the chamber, peering into the mist and steam of the broken cogitators, trying to pick out a flicker of movement.

He saw nothing – the creature’s chameleonic skin gave it perfect camouflage. They had to end this now, before the creature got to the magos. Cassius scanned the room, searching for something he could use. His bionic eye came to rest on a series of pipes that crossed the ceiling, separated at several points by small, hexagonal nozzles. He raised Infernus, flicked it over to its flamer mode, and sent a gout of fire across the roof of the chamber. Detecting the intense heat, the fire control system automatically activated, sending showers of water arcing across the room. He scanned his surroundings once more, trying to detect any unnatural ripples of movement in the downpour. Behind him and to the right, a few paces past the oblivious Brother Soemnus, the rain flickered slightly and changed direction, running in rivulets through the empty air.

‘There!’ he shouted, raising Infernus and wreathing the area with flame.

There was an unearthly shriek, and the towering silhouette of the creature drawn in the water flickered into corporeality, pale flesh and chitin seared and crackling. Still wailing in an unnerving, high-pitched register, the creature leapt over a bank of monitors, and, still burning, raced straight towards the magos. It was only ten paces away from the command console, raising its talons to strike.

Sergeant Verigar crashed into it from the side, slamming it into a cogitator desk, chainsword tearing at its flank. The lictor tried to bring its huge, scything talons to bear, but Verigar stayed in close, inside their reach. Instead, it struck at his helm with its feeder tendrils. The tentacles sharpened into spears, jabbing for the visor of the sergeant’s helm, trying to find a way into his skull. Its claws tore at the Ultramarine’s ceramite breastplate, and came away red.

Cassius ran forward and grabbed the xenos by its left talon-limb, roaring in fury as he tried to drag the heavy beast off Sergeant Verigar. It was too strong and too big for that, so he raised his crozius, found the joint of the creature’s limbs, and swung the mace hard, feeling the kick as the power field discharged. There was a splinter of bone, and the talon fell limp.

‘In the name of the God-Emperor, I purge thee, abomination,’ said the Chaplain.

His crozius fell once, twice, three times, caving in the lictor’s angular skull, pulping flesh and driving shards of broken chitin deep into its brain. It shuddered, twitched, and finally lay still.

Sergeant Verigar lay panting, his armour torn and bloody. Soemnus ran over to aid him.

‘Get him up, apothecary,’ said Cassius. ‘We must leave. Magos, are you done?’

Rothe pulled a switch on the main console, and the arm swung over to present the metal cylinders on its end to the deck. A segmented, tentacle-like mechadendrite extended from the sleeve of his robe and the claw on the end delicately removed one of the hand-length cylinders. Cassius saw now that the middle was transparent, and within he could see a clear liquid.

‘So this is our salvation?’ he said, watching the substance within roll and slide as Rothe made his way down the stairs from the command console. ‘This is how we deliver Kolovan from the xenos?’

‘I know you doubt me, Chaplain,’ said the magos, storing the sample within his robes, ‘but this will work.’

‘It had better,’ said Cassius, watching Soemnus and Kyvian haul Verigar to his feet. The Sergeant’s wounds were severe, and the Chaplain could tell from a glance that he would not fight on Kolovan again. ‘This planet has taken too much from our Chapter already, and I would have no more brothers lost for so little gain.’

Chapter Seven

Amongst the rolling hills of northwest Adverica, where waterfalls plunged from high plateaus and bright fingers of rivers formed fan-shaped deltas towards the coast, one of Kolovan’s enormous atmospheric processor facilities rose above the canopy of a sparse forest several kilometres inland. Station Thirty-Four was a field of vast, rectangular monoliths set into the ground at equidistant intervals, each one hundred metres high and covered with vents and grilles. Some way above sea level, the facility’s location had been chosen because the prevailing winds would carry its detoxified air along the greatest possible area of the populated coast.

From a distance it almost looked like a tenement hab-block had been torn straight out of the city and deposited in the middle of nowhere, though as the Stormravens of the Third Company came closer its industrial nature became more obvious. Pipes and thick cables were wrapped around each structure in heavy clusters and a rockcrete wall formed a defensive barrier around the compound. The road to the facility climbed a gentle slope and wound through a sparse but healthy-looking wood, which encircled the complex.

It was towards this station that the greater part of the Ultramarines headed, with as much speed as they could find on the cramped highways of the forest roads. Four squads of the Third, led by Cassius, would land in the transport gunships and secure the compound. Magos Rothe travelled with them. The facility was automated except for a skeleton crew of staff, enough to ensure the servitors and automated systems kept running. Attempts had been made to contact the occupants, but there had been no response. Geo-scans indicated that the area was free of tyranids, but they were taking no chances. Rothe would enter the main complex alongside Sergeant Verigar’s squad and Chaplain Cassius, and once inside he would begin the process of introducing the antiviral into Kolovan’s atmosphere. Soon after, the main convoy would arrive from the southern coastal roads, forming a defensive screen around Station Thirty-Four while the magos completed his procedure.

Before the Chaplain’s advance force rose the facility’s perimeter wall. Unlike most of the defences the Ultramarines had seen so far on Kolovan, this wall was intact and largely unmarked, a fifteen metre high circle of thick rockcrete with gates on each compass point. The lead armoured vehicles were already stationed outside of the main gate, which slowly yawned open before them. Rothe had handed over the facility’s secure entrance codes, and Cassius had decided not to ask where he had got hold of them.

‘No turrets or towers, but a great deal more defensible than I had anticipated,’ said Cassius, as his lead Rhino, carrying Regulus and the rest of Verigar’s squad, passed through the set of reinforced gates and into the field of processing towers.

‘That’s good,’ said Regulus. As the most senior battle-brother, he had taken on leadership of the squad in Verigar’s absence. Never the most jovial individual, his pale, morose countenance had been especially grim since the deaths of Brothers Haldus and Corrus. ‘The sky darkens. The tyranids have noted our movement. They will descend on this place in force.’

Galenus glanced out of the transport’s viewport. His battle-brother was right. The skies behind the task force were thick with spore-clouds and flyer-organisms, and they could hear the distant screeches of xenos further into the forest. They would be on the Ultramarines in minutes.

‘Escort me to the processing centre,’ said Magos Rothe, gesturing to a squat, wide prefab that lay flush with the northern wall of the compound, connected to the first row of filtration towers by a network of chrome piping.

‘Weapons ready, brothers,’ said Cassius. ‘If the enemy infests this place, we will not be taken unawares.’

They ran across open ground, the colossal towers looming over them on every side. Up close the noise they made was deafening, the roar of a thousand cyclones clashing together as air was forced through dozens of ionisation chambers. They stormed into the processing centre, a dank network of hissing pipes and ageing, worn cogitators. Descending from the ceiling were three pipes, each as wide as a Space Marine and capped with a series of grilles and levers. In front of these, on a raised platform, stood a bulky command console. Magos Rothe scurried up the rusted iron steps to the command platform, and began to withdraw a number of arcane devices from within his robes.

‘We don’t have time for your endless rituals,’ said Cassius. ‘Just get the job done.’

‘You must allow me time to perform the proper obeisance,’ insisted the magos, turning and brandishing a smoking censer. ‘This is a complex procedure, and we must ensure we have the Omnissiah’s blessing.’

Cassius watched with Brothers Regulus and Kyvian as Rothe began to emit a series of machine-code prayers. The devices involved were simple enough not to require the pacification of their machine-spirits. This ritual was one to the Machine God alone, for it was in the pursuit of complete knowledge – a holy objective of the Cult Mechanicus – that the antiviral strain had been developed in the first place. The air was thick with incense containing sacred elements, and the magos’ vocal unit crackled with a binary hymn.

The rattle of gunfire sounded in the distance, and Cassius’ vox-link hissed to life.

‘Lord Chaplain, the leading edge of the tyranid flyer swarm has reached our position. Request assistance,’ came the rough voice of Sergeant Hieronymar, who led the defence of the front gate.

‘I am on my way, sergeant,’ Cassius said. ‘Give them not an inch of ground.’

He cut the link and turned to Regulus and his squad.

‘I am needed on the field. Protect the magos, brothers, and we will strike a mighty blow against the xenos. Courage and honour.’

‘Courage and honour!’ they returned in unison.

As soon as Cassius had retrieved the antiviral sample, Galenus and Fabian’s armoured task force had retreated from the southern edge of Harienza, and taken the curving coastal road that ran north-west towards the processing plant. They were close to Station Thirty-Four now, but reports placed the tyranid swarm only a few kilometres behind their position. The convoy could not slow for a second, and not just because of the pursuit – reports had already reached them that Cassius’ strike team had engaged the enemy at the atmospheric processing plant, and the Chaplain did not have the numbers to stage an effective defence for long.

‘They should have cut us off in the city,’ voxed Captain Fabian. ‘Why didn’t they? We were exposed.’

‘I do not know, captain,’ Galenus replied. ‘Perhaps the death of the Swarmlord affected the xenos more than we know. I’ve rarely seen a tyranid host so slow to react.’

‘It was more than that,’ said Fabian. ‘The Harienza swarm was far smaller than we expected. There were few of the larger creatures coordinating enemy movement. So where is the main host?’

‘Does it matter?’ Galenus asked. ‘Their absence simply makes it easier for us to complete our mission.’

‘Perhaps. But I dislike not knowing what my enemy is thinking. I despise these wretched creatures.’

‘Contact!’ came the cry over the vox, cutting off their conversation. Galenus heard the chatter of storm bolters and the acidic hiss of projectiles splashing against the side of his vehicle. ‘Hundreds of flyers, circling the facility.’

‘Perhaps they’re not quite done after all,’ said Galenus, drawing his combi-melta. ‘It seems there are a few billion or so left to finish off. ‘

‘The good news is I’ve only the one hand left, my friend,’ Fabian voxed back. ‘So you should be able to keep pace with me today.’

Galenus laughed. He and his men waited impatiently for the transports to reach the gates of Station Thirty-Four, listening to the screams of lascannons and the roar of mounted bolters as the armoured force cut a path through to Cassius’ position.

Finally the Rhino swerved in a tight turn and the vehicle’s front ramp dropped. They had come to a stop outside the perimeter wall and formed a defensive ring of vehicles, a second wall that the enemy had to breach. The air outside was a frenzy of bat-like wings and bursts of bolter fire. Storming out of their transports, the Third and Fifth Company Tactical squads arranged themselves in compact formations, and began to pour fire into the flock of tyranids. The armoured vehicles faced outwards, ready for swift embarkation and egress once the antiviral had been dispersed. Their pintle-mounted bolters and flamers panned up to target the airborne swarm, and they added their own fire to the volleys of the beleaguered Ultramarines that guarded the facility’s walls and main gate. There stood Cassius, battering swooping, shrieking forms from the sky with his crozius and roaring his defiance at the enemy.

‘Remember Tarantua,’ he bellowed. ‘Remember the thousand Eldar that came screaming at us through the ruins of the Sculpted City. Remember that we broke them at dawn on the second day, a bloody sunrise that the alien will never forget.’

A winged creature dived at the Chaplain, and Cassius threw himself up to meet it, ignoring its slashing claws as he thrust the spike of his eagle-winged weapon through its skull. He bore the monster down under his weight, slamming his weapon into its twitching form again and again. He stood, covered in alien blood, and the roar from the nearby Ultramarines almost drowned out the cacophonous sound of beating wings.

‘Cassius!’ they chanted as they slew the enemy. ‘Cassius! Cassius!’

From the treeline came the first tyranid ground troops, no less numerous than they had been when the Ultramarines had first landed on Kolovan. The Predator tanks switched to prey-sense targeters to pick out the telltale heat signatures of massing hormagaunts and termagants. Their autocannons fired fragmenting shells that tore great explosions through the trees, turning the tough, dry wood into storms of splinters that shredded tyranids caught in the blast zone. It was not enough to turn the frenzied creatures back, and hundreds skittered over the two-dozen metres of open ground towards the Ultramarines infantry, swarming over the tanks as they came.

‘Battle-brothers of the Fifth Company,’ Galenus shouted, raising his power blade. ‘Time to forge new legends!’

In the face of the tyranid charge, the Ultramarines responded to aggression with aggression of their own, counter-charging right into the teeth of the enemy where a Space Marine’s strengths were magnified. The woodland was full of thunder and fury, the din of gunfire competing with the screams and howls of the attacking aliens. A rain of shredded foliage and splintered wood fell, and the air became thick with gunsmoke and noxious tyranid spores. The sky darkened, and Kolovan’s acid sun struggled to illuminate the bloodshed.

Devastator squads arrayed along the southern wall fired over the heads of their battle-brothers, thinning the numbers of the tyranid host with a torrent of heavy bolter fire. Those that carried plasma cannons and missile launchers saved their ammunition for the densest clusters of the enemy, or for the larger organisms that waded through the press.

Galenus fought in the front ranks and plunged his power sword into the chest of a towering tyrant-form that was screeching and urging its vile troops on. It tried to wrap a razor-edged tendril whip around his neck, but he pressed his combi-melta underneath its jaw and fired. The creature’s head was disintegrated in a super-heated flash of energy. The command squad around him surged forward in his wake. The Vindicators hurled ordnance into the treeline where fast-moving tyranid broods sought to encircle and outflank. A seemingly endless swarm of gargoyles flew overhead, striking at isolated sections of the Space Marine line, but the sheer volume of fire sent hundreds of them spiralling down to burst upon the ground.

To his left Galenus saw his friend Fabian standing on the smoking wreckage of a downed Rhino, roaring his defiance at the enemy and firing his plasma pistol in his one good hand. He couldn’t help but smile.

Deploying the biological weapon was a necessity, but Lord Chaplain Cassius was right – this was the only honest way to prosecute a war.

‘Not much to shed our blood for,’ said Brother Kyvian, indicating the black case cradled in the secondary manipulators of the servitor. Inside the case was the precious cylinder taken from the laboratory. From looks alone, the clear liquid inside could have been nothing more than water.

‘The magos maintains that it will decimate the xenos force,’ said Teriach.

‘If it works,’ said Morvion.

‘It will work,’ said Regulus.

‘I’ve rarely had the chance to observe the rituals of the Mechanicus,’ said Morvion, thoughtfully. ‘They do this every time they pull a lever?’

Magos Rothe had arranged his sacred oils on the desk of the command console, and they had shrouded the platform in a thick, grey mist. Through the haze of the incense and steam they could see his thin, orange-robed form, mechadendrites and appendage-tendrils extended like a cluster of snakes around him, adjusting dials, rewiring control panels and performing a thousand other complex tasks, the purpose of which entirely escaped the Ultramarines. All the while he hummed a low, static dirge, a binaric hymn of faith in the Omnissiah and in Holy Mars.

After several moments the magos’ chanting ceased, and he turned to the squad.

‘In the absence of menial servitors, I will require your assistance with the heavy labour,’ he said. ‘We will need to reconfigure the filtration system in order to achieve the widest possible dispersal.’

‘What do you need of us?’ asked Regulus.

‘Those primary conduits,’ said Rothe, pointing to an array of cylindrical ducts connected to the right-hand side of the building. ‘We must reconnect those to the central array in a specific configuration.’

Brother Morvion sighed. ‘Our brothers earn another glorious victory, while we rearrange some pipework,’ he said. ‘I think we should omit this from the squad’s honour scrolls, sergeant.’

Captain Fabian watched the Master of Sanctity as he burst forth from the gates of the compound to join the Third and the Fifth Companies’ assault. His anger at the Chaplain ebbed just a little as he watched him leap into battle, duck underneath the swipe of a tyranid warrior and bring his crozius up into its gut hard enough to lift the beast from the ground. Not slowing, he spun to the right, letting the momentum add power to a lateral swing that snapped the legs of another xenos, then raised his combi-weapon to wreathe an onrushing hormagaunt in flames.

‘The Fifth Company have the field,’ Fabian voxed to his Sergeants. ‘We take the towers and secure the complex. Squads four and five, to the eastern wall. Watch the perimeter, brothers. We cannot let them outflank us.’

Fabian jumped down from the ruined vehicle he had been observing the battle from, and winced as the impact sent a shock wave of pain stabbing through his ruined face. There had been no time to fit augmetics, but the captain had refused to contemplate staying out of the fight. Kolovan had taken a heavy toll on the Third Company, and he wanted to see this campaign through to the bloody end.

‘The Lord Chaplain is carving them apart,’ said Sergeant Gallo, and Fabian could hear the awe in his voice.

Before Kolovan, Fabian would have shared the sergeant’s admiration, but still he could not shake his disappointment at the Chaplain’s actions at Sigma Fortulis. For Cassius to preach so zealously of the wondrous Codex Astartes, then flagrantly ignore the primarch’s sacred work in order to pursue a personal vendetta…

Cassius insisted it had to be done, and Fabian knew well the stories of the Swarmlord’s power, but he could not see beyond the thirty-nine dead heroes he had left behind at the doomed fortress. It would take many years for the Third to recover from such a vicious toll. How many would still live, if the Master of Sanctity had been there to lead them, as his position demanded?

‘If the antiviral is successful, there will be none left to kill,’ he said. ‘He is making the most of things while there is still tyranid blood to shed.’

They both turned as a chorus of piercing hisses sounded from their left. Through a haze of smoke and drifting spores, Fabian could see three lumbering quadruped creatures on a raised mound of rock at the edge of the battle, each with a huge dorsal weapon-growth protruding from its back. As he watched, each growth began to glow with sickly green energy. As one, the creatures spewed forth a torrent of plasmatic flame, which roared across the clearing and struck the advancing Fifth Company squads in the flank. Ultramarines went down, vaporised completely or beating futilely at the green fire that melted their armour and flesh. Another blast took a Rhino in the side, and the super-heated flames cooked off its ammunition bay. There was a flash of searing light and a detonation that rattled the skull, and when the smoke cleared the vehicle was little more than a twisted sheet of blackened metal.

‘Brother Irilo,’ Captain Fabian shouted over the vox. ‘Artillery on the field. Fifty degrees left of your position.’

The Predator that the captain and his men knelt beside rumbled forward a few paces and rotated its main autocannon with the sound of grinding metal.

‘I see them, captain,’ came the calm voice of Irilo. ‘Engaging.’

There was a pause and then the cannon roared, blasting across at the artillery-beasts. Irilo’s first volley hit the central creature in its stocky forelimb, which burst apart in a spray of pale viscera. The xenos screeched and reared up, and the Predator tank put another shot through its torso, blasting it backwards to topple from the mound.

‘Fine shooting, brother!’ said Fabian.

‘My thanks, captain. Now get yourself inside the walls, we’ll take care of the rest.’

The captain and his men fell back, firing as they went. Another plasma blast from the remaining artillery-beasts slammed into the ground where they had been standing only moments before, sending up a geyser of broken earth but missing the Predator’s side armour.

Chittering flyers with membranous wings strafed Fabian’s men as they ran across the open ground towards the gate. Two brothers in front of the captain went down, flesh-tearing organisms spattering across their armour and grinding through the sturdy ceramite. Fabian sighted and fired a searing plasma blast into the face of one of the cursed things, burning its skull to ashes. Seeing their brothers rushing to support them, the Devastator squads of the Fifth Company ceased raking the tyranid’s ground force and turned their weapons to the skies.

Now it was not enemy fire that rained down on Fabian’s men, but the ruptured corpses of the flying xenos. Cheering, the Third’s Tactical squads poured through the facility’s towering gate. Without pause, the squads Fabian had assigned to the perimeter clattered up the access ports on the interior wall, while the rest of his men took up firing positions at the gate. Ahead, the tyranid flock whirled and regrouped for another attack run, bearing down on their position.

‘The tyranid wounded us at Sigma Fortulis,’ he shouted. ‘But even in their thousands they could not break us. Shall we show them what happens when you leave an Ultramarine still standing?’

As the tyranids dived to engage, the battle cries and bolter shells of the Third Company rose to meet them.

‘The foe is ahead of us,’ said Cassius, surveying the Ultramarines fighting to keep the treeline clear of tyranids. His voice was transmitted over the vox to all the nearby squads, including most of the Fifth Company and the nearest units of the Third. ‘They seek to surround and reduce us. But they are in error, for they do nothing but put themselves in our way. Brothers! Our course is clear! Follow the blazing beacon of your faith and drive the enemy before you!’

The two squads in the clearing, led by Sergeants Hieronymar and Matakelus, joined Cassius as he drew his crozius and ran for the treeline. Fleshborer fire thudded into Cassius’ armour but the artificer plates, which had been worn by a succession of Chaplains stretching back to the early Age of the Imperium, turned aside the incoming fire.

‘Ultramarines, advance and destroy!’ yelled the grizzled, white-haired Sergeant Hieronymar, whose reputation for surviving apparently mortal wounds was well-deserved. The battle-brothers charged as one as Cassius reached the treeline and ran right at a clutch of termagants that had appeared from behind a massive, vine-covered tree trunk.

Cassius had not allowed his mind to dwell on the losses at Harienza, nor Captain Fabian’s outburst following the mission at Sigma Fortulis. It would benefit him nothing to let his anger seethe and distract him from his mission priorities – he had set it aside, as he did fear and doubt, into that part of his mind created by sleep-teaching and meditation in the reclusiam. It was a mental prison, an oubliette where anything useless and harmful could be locked away to wither and die.

But even so, he could not deny to himself that it felt good to fight. This was an honest battle where there could be no excess of aggression, where every sword-blow and bullet was honourably struck in the Emperor’s name. Cassius took that wave of exultation in him and used it as he did every other weapon, making of himself the image of vengeance for the Ultramarines to follow.

He was their Chaplain. He was the master of their souls. It was his duty to inspire the Ultramarines, as the Ultramarines inspired the fighting men and women of the Imperium. And so he blazed a torrent of flame through the trees in front of him, and as the foliage was stripped away he singled out the biggest xenos lurking there, a tyranid warrior surrounded by slavering termagants.

Cassius could not pretend it did not feel good. He could not deny the hammering of his hearts and the flash of exultation as he knocked a tyranid aside and brought his crozius down into the midriff of the warrior.

It fell to the side and bolter fire slammed into it from the Ultramarines surging in behind. Cassius did not relent. With the synapse creature fallen, the termagants reverted to crude instinct, leaping in ones and twos at Cassius or fleeing before him. Those that tried to fight were shot down or batted aside – Cassius did not even activate the power field of his crozius to drive them back, relying on the strength of his arm.

And it was good. There was no enemy here who did not deserve righteous destruction. There was no obstacle that could not be overcome by the strength and aggression with which the Emperor had blessed His Space Marines. Cassius took that certainty and let it drive him on like an ocean wave.

‘Break them down!’ cried Cassius as he shattered the face of a termagant before a hormagaunt leapt at him through the leaves. Cassius dodged its claws, caught it by the throat and slammed it against the trunk of a tree. ‘They are nothing but mindless vermin to be crushed underfoot, unworthy foes for the sons of Ultramar!’

Cassius broke through a dense bank of twisted roots and branches, to see a knot of Third Company Ultramarines exchanging fire with an enormous hive tyrant. The creature wielded two roughly conical lumps of flesh covered in tiny orifices, which spat rapid fusillades of wriggling parasites that kept Squads Aridis and Traex pinned among the massive roots of a towering knot of trees.

‘Return fire!’ called Cassius over the local vox. ‘Buy me but a moment!’

At the sound of Cassius’ voice, Sergeant Traex snatched up the heavy bolter lying beside the wounded specialist of his squad, and stood proud of cover. Spores burst in sprays of thorny shrapnel around him as he blazed a volley at the hive tyrant. The xenos, which stood almost three times a Space Marine’s height, was caught by surprise and reeled as a dozen bolters were added to the weight of fire.

Cassius sprinted across the stretch of churned-up earth between him and the monster. The creature turned to him and tried to level its cannon at him, but Cassius charged right into it, crashing into its front knee with all his force and weight.

The Chaplain rammed his crozius into the tyrant’s knee joint. Its leg folded backwards and the tyrant fell to the side, one of its forelimbs grabbing a tree branch to steady itself. The Ultramarine did not relent. He struck the limb, knocking the creature down once more, and fired into its ridged thorax at point-blank range. Shredded chitin rained on his armour and a torrent of sickly pale blood splashed across his face. The tyrant writhed and screeched. Cassius stepped forward and brought his crozius down into the wreckage of its torso. There was another explosion of torn meat and bone as the power field flared, and the creature finally lay still.

Regulus heaved the conduit over his head, and slid it into the connector-grille. There was a satisfying clunk, and a hiss as the sealant-foam around the port activated and secured the airway. The central array now looked like a giant, mechanical heart, with the veins of the conduction tubes stretching across the chamber in a tangled but – at least according to Rothe – organised jumble. Beneath the cradle of pipework, the magos had installed a sealed plas-glass receptacle, connected to the main array.

The magos took the antiviral sample cylinder and placed it carefully into the receptacle. Then he took a step back to the console, and rested his metallic claw-appendage on a red, flashing rune.

‘Let this gift of knowledge be blessed by the Omnissiah most high,’ he said. ‘Let it purify the alien.’

He pressed down. The console rune turned a bright blue, limning Rothe’s half-obscured features in an eerie light. The entire room shook as the reconfigured filtration towers shuddered and groaned. There was a sound like rushing water, and the top of the antiviral cylinder detached. The pale liquid it contained rippled as it was siphoned off and vaporised, and then was released into the tower’s outflow conduits.

‘It is done,’ said the magos.

‘How long until it takes effect?’ asked Regulus.

‘Once infected, we should begin to observe the first symptoms in local organisms within three hours,’ said Rothe. ‘Once the enemy’s spore clouds have been exposed, infection rates will begin to increase exponentially. Within forty-eight hours, the entire planet will be rife with the antiviral. Any tyranid that sets foot on the surface will be infected.’

Regulus walked to the chamber door. Overhead the flock of tyranids had thinned considerably, their murmuration now erratic and ragged where once it had been unnervingly precise.

‘We’re beating them back,’ he said. ‘They’re losing cohesion.’

‘This is a desirable outcome,’ said Rothe. ‘If this cluster of bioforms embraces the individual survival instinct in lieu of the synaptic impulse, it will retreat back to the larger brood, carrying the antiviral with it.’

‘So now we wait,’ said Regulus.

Chapter Eight

The twin gunships of Peryton squadron circled Station Thirty-Four, then broke off to survey the surrounding terrain in opposite directions. Peryton Alpha passed over the patches of scorched and mutilated earth where the day’s battles had been fought, while Beta headed towards the region of deltas towards the coast.

That very second the pathogen was spreading out into Kolovan’s atmosphere, multiplying in the heat of arid Adverica, seething into every respiratory system and every biological network it encountered. The equations built into its genetic structure caused it to multiply with such voracity that the area for miles around the processing plant was saturated with the antiviral in minutes, even down to the soil itself.

‘Any contacts?’ voxed Cassius, as he surveyed the battle zone. It was quiet now that the tyranids had scattered. The aggression of the Ultramarines advance had torn its way through several of the specialised xenoforms that linked the tyranids’ hive consciousness. Deprived of their synaptic harmony, the simple-minded swarm creatures had embraced their animalistic survival instincts and taken flight.

‘Nothing as yet, Chaplain,’ came the vox from Peryton Beta.

‘I’m over the xenos retreat routes,’ voxed Peryton Alpha. ‘No obvious signs of sickness, no dead left behind.’

‘Keep looking,’ said Cassius. ‘Report any corpses you see.’

Captain Fabian nodded as Cassius approached. ‘This waiting pains me more than losing my eye did,’ he said. ‘Still nothing?’

Cassius shook his head. ‘No signs of illness or malady. Three hours since we dispersed the agent.’

‘We have passed your estimated window, magos,’ said Galenus. ‘Tell me it was not a mistake to rely on you.’

Magos Rothe looked up from his data-slate, which scrolled with meteorological data readings and estimations. His vox-grille crackled softly.

‘My readings confirm that the agent was successfully distributed,’ he said. ‘In fact, the sheer speed of its circulation exceeds our wildest estimations.’

‘Magos,’ growled Cassius, ‘what use is that to us if it does not kill what it is supposed to kill?’

Rothe said nothing, and simply lowered his gaze back to his datapad.

‘I warned you of this,’ said Cassius, turning to Galenus and Fabian. ‘I warned you against trusting the empty promises of scientists over the honesty of faithful combat. We have committed to two futile operations, when we should have taken the fight straight to the enemy’s heart.’

‘Perhaps the pathogen needs more time to work,’ said Galenus. There was an edge to his voice. He had been the champion of Rothe’s plan, and now he was seeing the hope it had promised evaporating in front of his eyes. Cassius looked to Magos Rothe, and the tech-priest’s steadfast refusal to meet the Space Marine’s eyes told him all he needed to know.

‘It should have worked,’ said the magos, quietly. ‘My calculations… the experiments… I must compile data from the deployment. There is much information. I require quietude to concentrate.’

The Ultramarines watched him shuffle off towards the nearest gunship. Fabian cursed, and shook his head. ‘What now?’

‘Gather your squads for embarkation,’ said Cassius, his words not permitting any questions. When he spoke as an authority, even the captains of the Ultramarines were honour-bound to listen. ‘We will head back to the landing zone and contact Shipmaster Vanheuten.’

They would require a new plan if the tyranids were to be halted on Kolovan.

No one ever needed to know how to cope with victory.

Victory was easy. Its celebration was its own end. It forged the bonds between brothers. It confirmed the lessons of strength, intelligence and unity taught from the seminaries of Macragge to the battle-lore repositories of the Ultramarines. The only concerns a Chaplain had were to remind the celebrants to spare thoughts for their fallen, and to ensure the lessons of the day’s battle were learned.

But defeat was another matter. The legends of the Space Marines did not allow for defeat. The Emperor’s finest did not lose – they overcame all odds, they vanquished any enemy, they prevailed when no mere men could. That was the image that was presented to the Imperium, the image cultivated and recorded in sermons and illuminations across the galaxy.

Defeat was not a part of the Ultramarines’ vocabulary. And yet while they still battled to save it, Kolovan already felt like defeat.

Cassius stepped before the congregation, which had gathered in the dusty landing zone of the Ultramarines’ base camp to hear his words. The glorious, gilded hall of the Chapel of Guilliman’s Ire onboard the Defence of Talassar would have been a grander backdrop for his oratory, but a Chaplain needed no such ornamentation to stoke the spirits of his warriors. The Third and Fifth Companies, both significantly reduced from full strength, knelt on the hard earth facing Cassius, their bare faces waiting for him to talk away the sting of their failure.

They could not have changed the outcome. They had fought as hard as any Space Marine could and they had never faltered in their duty. It was not their fault Kolovan was now condemned. But to tell them that would be to feed them a string of platitudes that no battle-brother could hear with respect.

‘We have all lost brothers,’ began Cassius. ‘Not just fellow warriors, but those to whom we were truly bonded. Those at whose side we have fought and faced death and triumph alike. Friends.’

Cassius’ eye passed over Brother Regulus, to whom Haldus had been a true brother. For all the stress the Codex placed on considering every fellow Space Marine an equal in battle, every Ultramarine had friends among those he fought beside. And many more than Regulus had lost such friends on Kolovan.

Cassius could tell them they would have revenge. But he had spoken enough of revenge already on Kolovan – revenge for their losses in the Tyrannic Wars, for all the human worlds devoured by the tyranids, for their fallen. And how, in truth, could anyone have revenge against the tyranids? Aside from the Swarmlord and the few rare leader-organisms that displayed a semblance of cunning, there was no suggestion of individuality to them. Killing a single organism meant nothing when it came to revenge. Unless an Ultramarine could kill the entire hive mind, it would be a hollow vengeance at best to kill even the mightiest tyranid.

‘In the peace and the dark, away from this place, we will grieve for them. As the ancient people of Macragge did when Roboute Guilliman walked among them, the contests of prowess and the pilgrimages to the places of the ancestors will be held to honour them. The pain you have now will be pooled, shared among us all, and through the dedication to the memory of our lost, will dissipate. Have faith that this is true, Ultramarines. It is the shield of faith that protects us in war. Now, it is faith that will see our fallen join the pantheon of our Chapter’s heroes.’

Cassius could see an unbreakable faith and devotion on the sea of faces before him. Some, like Morvion, did not disguise it. Others kept it hidden within them – but even Galenus and Fabian could not keep it from the glint of their eyes or the set of their jaws.

‘The time will come when your rage and hatred will be forged as hot and sharp as steel on the anvil,’ continued Cassius. He let his eye fall on each Ultramarine in turn, willing his words into their minds. ‘But it must not take root in you and blossom into a reckless and directionless rage. Do not deny it or crush it down. Acknowledge it as a part of yourself, and separate it from the rest of you until it is needed. Remember that like any weapon, your anger can be set aside until the time comes to use it. When that time comes, it will be ready for you, and the memories of your fallen will return to help drive the foe before us. Until then, place it alongside your bolter and combat knife, your chainblade and power armour, for when you need it once more.

‘And that time will come, my brothers. In this, above all other things, have faith.’

Cassius let his words hang in the incense-heavy air. Then he turned and left the brothers to offer their own silent prayers for the lost, and for victory on Kolovan.

‘Lord Chaplain,’ said Brother Regulus, approaching with his helm held under one arm. Cassius had made note of the man’s fine performance as squad leader since Sergeant Verigar’s injury, and intended to recommend him for promotion upon their return to Macragge. ‘We have received a communication from the shipmaster. He requests to speak to you.’

‘I shall attend,’ replied Cassius.

‘The sensorium helm noticed it two hours ago,’ said Shipmaster Vanheuten, his voice crackling slightly over the vox. ‘We had to wait until we cleared the horizon before we could look closer.’

Vanheuten had served in the fleet of the Ultramarines since adolescence, a noble son of Macragge given long ago by his family to the Chapter in tribute. The wavering holo-display revealed a severe-looking man, his peaked shipmaster’s cap topping a gaunt face with a steel-grey moustache and sunken blue eyes.

‘We’ve got data coming over from the sensoria now,’ continued Vanheuten. ‘I thought our magos might be able to shed some light.’

The servitors had set up a makeshift strategy centre in the largest of the landing zone’s prefabs, consisting of little more than a few benches and a holomat projector in the centre. Currently, it was rotating a two-dimensional tactical display that showed the position of the Ultramarines cruiser and the tyranid bio-vessels.

Cassius had been joined in the command tent by Magos Rothe, Captain Galenus, Captain Fabian and Techmarine Vorun from the Third Company. They all watched as the hologram flickered and changed, showing a grainy image of the void. A slice of Kolovan’s disc was visible, edged in harsh yellowish light. Above the planet floated four immense squid-like shapes of pale and bloated flesh, the largest of which was many times the size of the Ultramarines’ vessel. Its bulk was fringed with long, writhing tentacles, and enormous gills opened and closed along its length. From one end emerged a set of mandibles that guided strings of biomass into its gullet – biomass formed from the flora and fauna of Adverica.

‘The hive ships,’ said Galenus, with disgust in his voice.

‘The xenos have passed the tertiary harvesting stage,’ said Magos Rothe. ‘The spore chimneys must have been completed already for biomass to be ejected into orbit. Available data puts them well ahead of the standard model.’

‘Try to keep the admiration from your voice, magos,’ said Captain Fabian.

‘One must appreciate the capacity of the xenos to better counteract them,’ replied Rothe.

‘There,’ said Vanheuten. ‘See it? That ugly damn thing in the bottom left of the display. Keep watching.’

Vanheuten indicated a smaller ship, one of the largest hive ship’s calves. The two smallest calves were spooling up the clouds of biomass ejected from the planet, then spitting it in coherent ropes to the hive ship, but this calf looked different. It rolled out of the shadow of the hive ship revealing a dry and mottled surface with patches of skin flaking away to reveal stringy grey matter beneath. As the strike force commanders watched, the calf veered awkwardly, almost crashing into the side of the mother ship as it tried to compensate for the sudden course change.

‘What’s happening to it’ asked Fabian.

‘It’s coming apart in the upper atmosphere,’ said Vanheuten. ‘It’s still mobile, but its movement is erratic.

‘The pathogen,’ said Galenus with relish. ‘It infected the biomass. We did poison it after all!’

‘But it did not affect the organisms on the surface,’ said Cassius. ‘Magos?’

‘A hypothesis suggests itself,’ said Rothe, and for a moment Cassius thought he heard something as human as excitement in the magos’ voice. ‘We can assume, given its location, that this force is an off-shoot of the shattered hive fleet designated Kraken, but its presence has not been recorded before. Isolated from the greater tyranid host, we have no idea where it has been or how the fleet’s bio-construction capability has been affected or altered.

‘So the genetics of these creatures may have been altered so completely that the pathogen you developed no longer affects them?’ said Galenus.

‘Indeed,’ Rothe replied. ‘Why, then, do the ships appear vulnerable to the agent? I would posit that while the tyranid ground troops have been genetically altered via the bio-construction process to the extent that they are immune, or perhaps merely highly resistant, the hive ships themselves retain enough similarities to the Kraken genus that they do not share this resilience. If this is the case, the pathogen may still possess lethal capacity against them.’

‘If we kill their ships we can trap the xenos on the surface,’ said Galenus. ‘They’ll never leave Kolovan and the fleet will never breach the Segmentum Solar. The whole invasion will stall.’

‘The reasoning is sound,’ agreed Rothe.

‘Can we replicate the pathogen and launch it directly at the mother ship?’ asked Galenus.

‘I have retained only a small sample,’ said Rothe. ‘And the hive calf was maimed by infected biomass. Our limited knowledge of fleet organism biology suggests it took that material deep within itself to digestive and reconstitution organs before it was regurgitated to the parent ship. A torpedo is unlikely to penetrate deep enough to ensure full infection, especially against the larger organism.’

‘Then what do you suggest?’ said Fabian.

‘He suggests,’ said Cassius, ‘that we ready a ship full of Space Marines for a boarding action. A small task force could breach the outer membranes, and deliver the agent directly to a vital organ.’

‘So we take the pathogen onto the hive ship and inject it right into that thing’s heart?’ said Fabian.

‘Technically the circulatory organ is known as the energy cortex,’ said Rothe, ‘though its function is essentially the same. As you might imagine, however, data regarding the interior of tyranid bio-vessels is scarce. I am unable to provide reliable guidance as to where the organ might be located.’

He rotated his augmetic limb, thoughtfully.

‘I will head to my transport vessel,’ he said. ‘I have enough equipment stored onboard that I believe I shall be able to come up with a solution.’

The holo-image of Vanheuten leaned forward to press something, and the tactical display changed once more.

‘I’m afraid there is another complication,’ he said.

‘You jest,’ said Fabian, drily.

‘When you informed us that resistance in Harienza was slighter than expected,’ the Shipmaster continued, ‘I had the crew perform another orbital scan. The results are worrying.’

The hologrammatic display zoomed in. It centred on the cluster of coastal cities to the north of Harienza. Brown stains covered the image, and as the display came into focus, the Space Marines saw what had Vanheuten so concerned.

‘The tyranids have finally established their digestion pools and capillary towers on Adverica,’ said Vanheuten. ‘They appear to be processing Kolovan’s biomass, and far quicker than we anticipated.’

‘Where is this?’ asked Cassius.

‘Mesa Varenus,’ replied the shipmaster. ‘The northernmost and most populous city on Adverica, along the coast from Harienza. The city itself was hit hard. It’s little more than rubble. And those damned things.’

He gestured to the display. The once-proud centre of Mesa Varenus had been scoured by the xenos, and now a cradle of iron skeletons that had once been hab-blocks formed a ring around their vile bio-constructions. Barbed spirals of bone reached to the sky, clawing free from colossal pits that pockmarked the surface of the planet like festering sores. These craters swirled and rippled as tyranid organisms writhed below their foul waters. The enemy was present in unthinkable numbers. The image quality presented them as a constantly shifting carpet of flesh, insects flocking to an open wound, though Cassius knew there would be a horrifying precision to their movement. Tiny digestion organisms, full to bursting with the dead flesh of Kolovan, would hurl themselves into those digestion pools to be dissolved in turn, adding yet more biomass to the rancid gruel that would be siphoned up via the organic towers and consumed by the hive ships. Nothing would be wasted, and when the process was complete the fleet would move on, leaving the planet as nothing more than a lifeless husk.

‘This was why the forces we encountered at Harienza and the filtration plant were fewer in number,’ said Galenus. ‘The main enemy force guards these structures.’

That force dwarfed anything they had encountered on Kolovan so far. It was a swarm that had killed a planet, and would do so again unless they stopped it here.

‘We must bring these towers down,’ said Cassius. ‘Time is short. If we tarry, the tyranid fleet will gorge itself and move on to the next Imperial world. My strike team will make all haste to administer the pathogen, but we do not know how long that will take. The Third and Fifth must fight together again.’

‘Can we not simply obliterate this abomination from orbit?’ said Fabian. Cassius could hear the hatred dripping from his every word. Such emotion was not something one usually associated with the easy-going, popular captain. Perhaps he was finally learning.

‘We could begin bombardment,’ said Shipmaster Vanheuten, ‘but that would draw the attention of the hive fleet. Currently we’re powered down and secure in low orbit, but they would certainly notice us if we opened fire. The size of those ships… the Talassar’s a tough old bird, but she won’t last long against that.’

‘On the ground, then,’ said Galenus.

The two captains shared a glance, and nodded. The calculating tactician and the charismatic leader of men. Cassius was reminded, not for the first time, why he had chosen Galenus and Fabian for glory, all those years ago. In their own way, each represented the ideals of the Ultramarines.

Other Space Marine Chapters, less secure in their identity and holy purpose than the sons of Guilliman, denigrated the Ultramarines as unthinking adherents to the blessed Codex, devoid of personality and individuality. Such thinking was beyond contempt. One only needed to observe the noble wisdom of Chief Librarian Tigurius, the fury of Cato Sicarius or the cunning of Scout Master Telion to know as much. Together his battle-brothers were bound by their reverence for the greatest military and spiritual treatise ever written, but that did not erode their sense of self. Rather, the primarch’s writing allowed each man to realise his own strength, and to bring it to bear as part of the greatest fighting force that the galaxy had ever seen.

‘We will need our full strength to destroy those feeding towers,’ said Fabian. ‘The Dreadnoughts must be roused, and we must commit every fighting vehicle, every brother still capable of holding a bolter.’

‘A hard and fast assault,’ agreed Galenus. ‘My company will approach the city from the west, across the open ground.’

‘And the Third will push from the south, through the destroyed industrial zones,’ said Fabian, gesturing to a clustered hell of ruined factories and destroyed work yards that formed a rough semi-circle around the tyranid feeding structures. ‘We will bring those towers down, and cut into the flank of the enemy force.’

‘I will take the remaining veterans to the enemy hive ship,’ said Cassius. ‘A small force will have a better chance of avoiding the enemy and locating the target.’

There was a silence.

‘I am trying to decide which of us has the lowest odds of survival,’ said Fabian. ‘I think it’s roughly even.’

‘We will not fall here,’ said Cassius. ‘When we leave Kolovan the Third and Fifth Companies will have won a glorious victory to inscribe upon their honour scrolls to rival the conquering of Damnos or the purging of Magnor Primaris. And the galaxy shall know that every brother who fell here died to preserve the souls of untold billions.’

‘No Ultramarine could ask for more,’ said Captain Galenus. ‘I must gather my men. I shall see you in the field.’

He struck a gauntlet to his chest in salute, and then departed the command tent, a swirl of ash rushing into the building as he opened the prefab door. Shipmaster Vanheuten made the sign of the aquila and cut his holo-connection, and Cassius and Fabian were left alone. The captain flexed his augmetic hand, a gauntlet of polished steel that would suffice until a more sophisticated replacement could be attached. His missing eye had also been replaced with a bionic not entirely dissimilar to Cassius’ own, though Fabian’s had been hastily affixed to his eye socket with a series of splayed metal staples, and looked vaguely insectoid.

‘I wish you fortune, Lord Chaplain,’ he said. ‘Truly. We may have our differences, but I know you will get this done.’

‘As do I, Captain Fabian. Strike hard and fast, and give your enemy no opportunity to recover,’ said Cassius. ‘As the Codex states.’

‘Courage and honour, Cassius.’

‘Courage and honour, captain.’

Chapter Nine

There was neither celebration nor sorrow among the Tyrannic War veterans when they were roused from their cells and duelling circles, and summoned to the muster deck of the Defence of Talassar. They did not express joy that they were going back into battle nor anger at the losses inflicted on their number at Sigma Fortulis. There was only a sense of purpose and determination that accompanied them as they gathered on the cavernous muster deck. It was unvoiced, of course, but Cassius could read it in his battle-brothers as if it had been inscribed on their armour.

‘I thought I’d killed my last tyranid here,’ said Brother Etriades as he took his place alongside the others. The fact that he was standing at all was astonishing. The wounds that he had suffered under the blades of the Swarmlord had been vicious, but none had managed to keep him in the medicae. His missing leg had been replaced with a cumbersome, claw-like bionic and his armour had been hastily repaired, though great gouges were still torn across the greaves and chestplate.

With some reluctance, Soemnus had cleared him for duty. The Apothecary had also been seconded to the assault team, and now stood eyeing Etriades warily, his chainsword in hand. Soemnus had served a term in the Deathwatch, the chamber militant of the Ordo Xenos, and Cassius had welcomed his experience of tyranid biology.

‘None of us have killed our last tyranid,’ said Sergeant Remas. ‘There are always more.’

‘Not always,’ replied Brother Pharron. ‘One day, they will be gone. We won’t be here to see it, but we will prevail.’

‘Or we will live through mankind’s death throes,’ added Kilrian, ‘and go down fighting as the Kraken devours us. Either way, we fight.’

‘That’s the spirit, brother,’ said Brother Errath. ‘Nothing like an optimistic frame of mind.’

Metal clicked on metal, and Cassius turned to see Magos Rothe, heading towards him, clutching a pair of devices in his hands. One was a small, steel cylinder, with an open gap in the middle through which a pale, swirling liquid could be seen. The other was a device that looked much like an auspex, though bulkier and rough-edged, as if it had been hastily constructed from whatever spare parts came to hand.

‘Lord Chaplain,’ said Rothe, presenting both items. ‘I have made some calculations, and I believe I have a way to help you locate the hive ship’s energy cortex.’

Cassius took the pathogen vial and handed it to Soemnus. The other device was heavy in his hands. As he held it, he noticed a series of pulsing readings scroll across its data-screen.

‘This is a customised dosimeter,’ said the magos. ‘It will locate and track large pulses of energy in the immediate vicinity. I have programmed it according to the latest data that the Adeptus Mechanicus has obtained regarding tyranid bio-vessels, but it will not guide you directly to your objective. Rather, it will keep you heading in the right direction. Operation could not be simpler.’

He point to a brass button on the side of the device.

‘This switches it on,’ he said.

Cassius heard Etriades snort with laughter. Rothe glanced back at him in surprise.

‘Once it is active, the process is automated,’ he continued. ‘It is a crude device, but given our limited time span it is all I can offer you.’

‘My thanks, magos,’ said Cassius.

Rothe lingered, burbling softly in binaric.

‘May the Omnissiah guide your steps, Chaplain,’ he said at last. ‘Our time together has been… illuminating.’

‘We are departing imminently,’ said the Chaplain. ‘You should vacate the muster deck.’

‘Your chances of success would appear to be minimal,’ said the magos, finally. ‘But I believe you can complete your mission. I have witnessed the Ultramarines in battle, and they are capable of subverting even the most vicious odds.’

‘Commencing approach vector,’ came the artificial voice blaring over the ship’s vox-casters. ‘All crew to stations, stow and brace.’

‘Let’s get this suicide mission underway then,’ said Kilrian.

The strike team filed into the nearest of the boarding torpedoes that were arrayed facing the muster deck’s enormous blast doors. Each torpedo was a huge cylindrical vehicle with clusters of engines around its stern and midsection, and multiple drill heads on its prow like the gnashing teeth of some enormous parasite. Each had the name of a fallen champion of the Ultramarines stencilled on its hull, as if those long-dead Space Marines were striking a final blow against the enemy.

Cassius joined the veteran squad in embarking onto their boarding torpedo. It was as cramped inside as the drop pods the force had used to assault Kolovan.

‘Twenty-one or twenty-two?’ asked Errath as the squad bolted in to their restraint harnesses. He gave Etriades’ augmetic leg a kick, and there was the dull clunk of ceramite on steel.

‘Twenty-one,’ said Remas. The rest of the Veterans nodded in affirmation.

‘Dare I even ask?’ said Apothecary Soemnus.

Kilrian chuckled. ‘Brother Etriades’ noble left leg is the twenty-first limb to give its life in defence of the Imperium from the tyranid menace since the inception of Veteran Squad Remus,’ he said. ‘We go through them almost as quickly as we do battle-brothers.’

The torpedo shuddered as the deck’s blast doors opened outside. Inside, each torpedo was little more than a steel tube with several restraint harnesses, now lit red by the warning strobes that indicated an imminent launch. The Ultramarines put on their helmets and strapped themselves in to the grav-compensator rigs along the side of the troop compartment.

‘Thus we first ventured to bring war to the stars,’ said Cassius. ‘As Guilliman and the Emperor led us in the Great Crusade. Thus we were created, to fight in the void as no man could. Now those ten thousand years vanish and we fight as those first of us did. The foe has changed but we have not. Our ancestors fought with honour and fury, and mercy to them was a sin. And just as they taught the galaxy to bow before the Emperor, so we shall teach the Kraken to know fear.’

As one, the Tyrannic War veterans struck gauntleted fists to their breastplates.

‘For Macragge and for Sotha!’ they roared. That was all that was said. That was all any of them needed to remember.

With stomach-lurching force the rear engines fired. The torpedoes sped towards the starboard side of the hive ship and the slits in its skin that Vanheuten’s crew had identified as likely gills. There were few obvious ways into the hive ship and the jaws were out of the question given the forest of feeder tentacles that surrounded them. The colossal tendrils would snatch up any foreign objects that strayed within range and drag them into the vessel’s maw to be digested. The dorsal organism pits and the gills were the strike force’s best chances, but they offered a probability of success well below certainty.

So much was up to chance. Guilliman had written in the Codex Astartes of the perfect battle for Space Marines to fight – an isolated or unprepared enemy, vulnerable to the surgical strike with overwhelming speed and strength. It was for such a battle that they had been created. But Guilliman had also written of the imperfect battle, where they did not have the luxury of perfect intelligence, a choice of battlefield or an ignorant enemy. There, it was the valour and discipline of the Adeptus Astartes, their aggression and toughness, that would see them through.

This, Cassius was certain, could be classed as an imperfect battle.

‘The Kraken took Sotha and left nothing but dust and ash behind,’ said Sergeant Remas. ‘Every surviving brother swore their own oath of vengeance against the enemy. I know I am not truly a brother to any of you, but hear my oath now. I will not stop fighting until every tyranid is dead. I know this means I will die fighting them. This I welcome, for there is nothing left in this galaxy now but a death in pursuit of my vow.’

‘You seek death,’ said Fandralus.

‘If you see it like that,’ replied Remas. ‘Take it or scorn it. It is said.’

The torpedo shuddered and the thrusters tilted it onto its final trajectory, aiming for the dark slashes in the vast organism’s side.

The hive ship dwarfed the Defence of Talassar. It was bigger than the mightiest Imperial battleships. Getting lost inside, far from any vital organ, was one of the biggest dangers the Ultramarines faced.

‘Final approach,’ came the synthesised voice of the servitor-pilot. ‘Brace. Brace.’

The lighting in the torpedo went dark. The crude vessel shuddered as the retro-firing engines burned. What followed was a moment of total silence as the engines cut off completely, relying on the optimum inertia of the torpedo to carry it through the last few hundred metres of void.

Cassius could hear the twin drumming of his hearts – one human, one a gene-cultured augmentation.

A sudden scream told him the prow grinders were active. Their note changed as they struck flesh and Cassius’ restraints fought to keep him from being flung free by the deceleration and the sudden impact. His stomach lurched, even his transhuman physique battered by the violence of the breach.

Warning runes flickered from the readouts on the walls. An alarm tone warbled from the prow. The grinders continued, the sound deepened by the greedy gurgle of flesh being chewed through.

Then the grinding halted. The alarm sounded for a few moments, then cut out.

‘Ready yourselves,’ said Cassius. ‘Think of our brothers on the surface, and know that if we fail here they will surely die.’

With a shriek, the torpedo’s prow was forced open into three petals of gore-coated steel. Into the torpedo rolled a toxic miasma of poisons and spores, the foetid exhalation of the Kraken. Warning runes flicked on inside Cassius’ helmet as its filters were pushed to maximum.

‘Throne alive, that stench,’ snarled Brother Kilrian.

‘Just be grateful you can breathe it,’ said Tiresis. ‘If our filters can’t cope we’ll be running on internal oxygen. That will cut this mission very short indeed.’

‘Then we’d better kill it quickly,’ said Pharron, thumbing his combi-weapon over to its flamer setting and briefly sending a soft orange light dancing across his armour.

The Ultramarines unbuckled their restraints and the flashlights mounted on their shoulder-plates illuminated the interior. The torpedo had entered the hive ship’s gill and bored through several layers of whalebone-like material to reach a cavity inside. The walls were covered in fine whitish cilia and irregularly-spaced breathing orifices that opened and closed like dumb mouths. The passageway continued up ahead, joining the honeycomb of the hive ship’s lungs.

The gravity was low. This high in orbit, Kolovan’s mass had only a slight effect. Cassius had to kick himself off a wall to get clear of the torpedo’s opening and arrest his motion by digging an outstretched hand into the soft, mucusy substance of the wall. Space Marines were trained to fight in low gravity, but it was still far from the Chapter’s standard mode of battle.

‘There is rhythmic energy activity towards the prow,’ said Apothecary Soemnus, studying the dosimeter. ‘Powerful activity. From the readings I would suggest we head that way.’

‘Then we move,’ said Cassius.

‘General advance, full spread!’ said Remas over the vox. ‘And keep your eyes open. Every corner could be a threat.’

The veterans led the way through the heaving, fibrous mass of the hive ship’s interior tunnels. They moved rapidly through the minimal gravity, pulling themselves along by the hair-like cilia covering the walls. The old training in zero-gravity environments over Macragge returned to them rapidly as they half-marched, half-swam through the confines of the hive ship.

Minor organisms, pale finger-sized worms or flittering insects that trailed long tendrils, fled as the Ultramarines passed. There was no telling how many billions of organisms lived inside the hive ship, specialised to function like the cells in a human body. And just as the body reacted to fight infection, so the ship would fight the Ultramarines.

‘Contact!’ came the cry from Brother Pharron, at the tip of the formation.

They were passing through a narrow membranous corridor, wide enough only for them to advance single file. Cassius, third in formation, could not see what was approaching, but he heard the roar of his combi-flamer and heard an alien screech of agony.

‘Contact!’ voxed Brother Tiresis, bringing up the rear. More sounds of battle reached the Chaplain’s ears, this time the acid hiss of enemy bio-weapon fire, and the crack of a power weapon impact.

Cassius cursed, unable to move forward or back, but desperate to engage the enemy. He did not have to wait long. A wicked, arm-length blade slashed through the membrane wall before him, and curtains of flesh peeled back to reveal several tyranid warrior-forms, pale and sickly-looking, loops of mucal slime trailing from their bodies to the wall of the cramped channel through which they came.

Cassius aimed Infernus at the chest of the leading creature and opened fire.

‘Holy Throne,’ whispered Brother Lyrun.

Mesa Varenus, the most populous habitation centre on the continent of Adverica, had been efficiently wiped from the face of Kolovan. Once, its bustling streets would have been thronged with citizens on their way to another day of hard labour in the belly of the great factory-blocks, or to offer their midday prayers in the sprawling temple district. Looking at what now remained, it was hard to believe that just a few weeks ago it had been a functioning Imperial city.

Up close, the capillary towers that the tyranids had created were horrifying in scale. They reached so high that they pierced the swirling clouds of spores that hung over the city, stretching and curving upwards like barbed, arachnid legs. On the open ground below the towers, Galenus could see the repulsive digestion pits, great lakes of grey-brown liquid that bubbled and frothed with chemical activity. So close to the city the sky was dark and clouded, striated with pale fingers of toxic yellow light as Kolovan’s sun stubbornly tried to pierce through the nightmare that had enveloped the planet.

Everywhere they looked, the enemy writhed. The hormagaunt infantry-forms were so numerous that it was impossible to pick a single creature out from the sea of off-white flesh. Tyrant-forms stalked through the swarm of bodies, and great, four-legged feeder organisms spewed fresh slurries of biomass into the pools of broken-down matter.

‘There must be millions of the cursed things,’ said Brother Dariun, peering out of the command Rhino’s viewing port.

The Fifth Company was stationed behind a ridge roughly a kilometre from the city and the tyranid feeding structures. Ahead of them was a flat, dry plain of cracked earth, perfect terrain for an armoured assault. There was no time for a complex tactical approach – the full force of the company’s tanks had been drawn up to lead the assault, while the Rhinos containing the Tactical squads would follow behind, discharging their cargo of Ultramarines right into the gut of the enemy force.

‘When Captain Fabian is in position we will be across that plain and into their ranks before they even realise they are under attack,’ voxed Galenus, addressing the entire company. ‘Do not stop, not for a single moment. Victory here depends on our momentum. We must strike hard and break through to the towers before the enemy can mount an effective defence.’

‘Captain Galenus,’ said Sergeant Kytheos. ‘The Third is in position. Captain Fabian awaits your signal.’

Galenus nodded. ‘Let us begin,’ he said.

‘All units, advance, cruising speed!’ Kytheos shouted.

‘Flamers to the fore!’ shouted Cassius. ‘Burn them to ashes!’

Cassius flicked the fire selector on his own combi-flamer just as a hideous six-limbed creature rounded the corner before him. Genestealer. The tyranid species was an enigma to the average Imperial citizen, but stories inspired by this particular xenos beast had been propagated on a thousand worlds. Tales of entire populations disappearing one by one, dragged into the darkness by razor-sharp claws, tales of terror and bloodshed. Some of these whispered nightmares were embellishments, exaggerated to scare mortal children away from dark and dangerous places. Some were not.

The creature leapt at Cassius, and he torched it in mid-air, turning slightly as he did so to let its burning, screeching body crash past him. He turned to finish it, but saw Sergeant Remas set himself and swipe his sword across in a vicious backhand slice. The genestealer’s smouldering head came free and its corpse toppled into the ankle-deep fluid that seeped into the chamber.

‘We’re lost, Chaplain,’ Remas shouted as Pharron and Kilrian rushed past, sending sheets of flame down the hall before them. ‘Soemnus says the signal is growing weaker again.’

There was no time to reply. More genestealers slithered from access cysts in the low ceiling, dropping with a splash into the filthy liquid and scrambling towards the Ultramarines, wicked claws leading.

Sergeant Remas blasted away at one with his bolt pistol, but they were damned fast. Cassius saw him go down, sending up a great gout of brackish liquid as he fell. The other went straight for the Chaplain. He stepped back, accepting a slash on his forearm from the creature’s serrated foreclaws. Its second set of arms swept at his belly, trying to open up the ceramite and spill his guts. Cassius jabbed his crozius forward, letting the winged tip of the weapon crunch into the genestealer’s face.

His enemy’s swing missed, and it rocked back, staggered by pain as one of its hateful, deep-black eyes dripped down its angular jaw. Cassius did not waste a moment. He flicked Infernus back to its default fire mode and shot the creature in the face. Bone and blood sprayed across his vision. He turned to help Remas and saw the Scythe of the Emperor pull his power blade free from a dead genestealer’s skull. Cassius helped the sergeant to his feet.

‘We have to move,’ Remas said. ‘If we halt, they surround us.’

Cassius growled in frustration. Wherever they ran, the enemy found them, and they had no idea how close they were to the energy cortex.

‘We push forward,’ he said. ‘There is no turning back.’

That was a practical point as much as a metaphorical one. Genestealers and warrior-forms harried the rear of the squad, pouring from chambers that the strike team thought cleared. Second-guessing their original decision to head towards the maw of the ship would only slow them down and allow the tyranids to cut them off completely.

The squad reformed, Kilrian and Pharron pushing ahead through the tattered remnants of a wall-membrane into the next arterial channel, flamers leading the way. Here the flesh-walls were near a hundred metres in height, stretched so taut that they looked almost human in design. Only the faint ribbing of what looked like capillaries running along the channel, and the faint, rainbow shimmer of chemically reactive lighting gave away their organic nature. That and the smell, though the entire ship reeked to Cassius, even through the filtration mechanisms on his rebreather.

‘Clear,’ said Pharron, flicking his combi-weapon back to the bolter mode. He and Kilrian moved forwards, faster now.

There was a sound like tearing cloth, loud and coming from behind the Ultramarines. Cassius turned.

Behind them, near the membrane they had entered through, the flesh-walls had torn open at floor level, releasing a flood of milky-white fluid. The rent in the skin of the ship was tearing towards them, and through the gap poured a tide of slavering, fist-sized organisms with barbed, tapered bodies, each of which culminated in a yawning, fang-filled mouth.

‘Rippers!’ yelled Brother Tiresis, and Cassius heard the roar of his plasma pistol as he fired into the swarm of bodies. ‘Move!’

Thousands of them bore down in a living wave, filling the channel as if the hive ship were drowning in a sea of them. The tear in the flesh-wall outpaced the Ultramarines, and suddenly the tide of organisms was in front and to their flanks, as well as behind. Cassius fired a prolonged gout of flame into the mass and in the low gravity it flowed like water, sluicing up the chamber sides, billowing like incandescent smoke as the walls blackened and flaked away.

The wave hit him. He was aware of Brother Etriades beside him, slashing with his twin chainblades. The burning mass of rippers swamped Cassius and he swept around him with his crozius, letting the power field erupt to blast a hole in the solid mass of writhing, biting bodies.

The vox was alive with curses and grunts of pain. Someone screamed.

‘Squad!’ came Remas’ voice. ‘To me! Grenades away!’

Cassius fired again and the flame washed back over him, rebounding off a solid mass of the diminutive creatures. He kicked off the wall beside him and slammed into the opposite one, the lung tissue giving way beneath his impact. Rippers were crushed and fell aside. Cassius rolled in place, trusting in his armour to hold against the flames and struck out again with his crozius. He could see nothing but the segmented limbs and flesh-tube bodies of the rippers trying to chew through his faceplate. The only sound aside from the vox was the grinding of tiny jaws against his armour, his own breathing and the hammering of his hearts.

Frag grenades burst all around. Cassius batted more rippers with his crozius and saw a hand reaching for him. It caught him around the collar and dragged him out of the tide. Cassius glanced round to see Brother Kilrian hauling him clear, firing his combi-flamer one-handed into the swarm. Dozens were caught in the spray of fire, and the blackened walls of the lung chamber crumbled into a haze of black-grey ash.

‘Keep moving!’ ordered Cassius, clambering back to his feet.

The veterans had thinned the first wave of rippers. Morvion’s chainblade was already trailing streamers of shredded muscle and the air was full of torn flesh and blobs of ichor. Cassius could see only a couple of metres through it – even Kilrian beside him was just a shadow against darkness.

They were blind. Blind and surrounded, in the belly of the foe.

The door-membrane at the far end of the corridor had sealed. Cassius made to strike it with his crozius, but Brother Errath put a hand on his shoulder and stepped forward with his multi-melta. He blasted streams of white-hot energy into the fleshy substance, and it warped and melted in the unimaginable heat. Errath kicked through the charred and twisted remnants, and Cassius could see more clearly as the veterans forged up a gently sloping mound of muscle, with pale blue, pulsing glands hanging from the ceiling like stalactites. Ahead, the ceiling rose sharply, and Cassius could see more of the strange growths hanging a few dozen metres above. Across the floor were spread several strange shapes, like fleshy petals, splayed across a hole in the chamber floor. These pulsed with the same blue energy as the growths, and they curled inwards slightly as the Ultramarines came forward.

Kilrian entered the room, bolter sweeping to the left. As he brought it back across, a pale white blur slammed into him from the right, bearing him to the floor. Ceramite screeched as the genestealer dug its claws into Kilrian’s back, scratching, rending and tearing. Blood sprayed, and Cassius heard the snap of bone. He rushed to his stricken battle-brother and slammed his crozius into the genestealer’s skull. It collapsed, twitching, on top of Kilrian.

He turned, looking for Apothecary Soemnus, and something slammed into his gut with fearsome force. He folded and was forced backwards. He felt claws digging into his armour, into his flesh. He could see the genestealer’s stinking, snarling face and smell its rotten breath. He tucked his legs behind its own, holding the creature close and trying to bring it down, trying to angle his bolter to put a bullet through it. Something sharp tore into his side and left a searing shard of agony in his flesh.

He headbutted the creature, once, twice, and then they were rolling, clawing and punching at each other. Something else grabbed at his leg, and he roared in fury as he felt its powerful strength wrap around his body and drag him across the floor. Distantly, he could hear the deep thud of bolter shells and the battle-oaths of his brothers. Still he was pressed together with the genestealer, and as it snapped and screeched in his face, he saw a thick fold of corded muscle wrap across them both, enveloping them in a cocoon of stinking xenos meat.

Cassius suddenly felt a constricting pressure so great that he thought every bone in his body would break. Then the darkness claimed him.

Roaring his faith in the Emperor and his love of glorious Ultramar, Captain Fabian charged across the shattered remnants of Mesa Varenus at the head of the Third Company.

‘Forward to glory, brothers of the Third!’ he roared. ‘First to battle! First to glory!’

To their left, Galenus had crashed into the tyranid ranks, lascannons and autocannons blasting ceaselessly as the two formations of tanks peeled left and right, forcing a gap into the enemy force through which came the infantry in their armoured vehicles. The ramps came down and disciplined Ultramarines squads emerged, marching in tight formations that punished the massed ranks of the enemy with ceaseless volleys of mass-reactive rounds. As they advanced, the tanks and artillery pieces began to hammer the thickest clusters of enemy organisms. The three Vindicator siege tanks, meanwhile, slung high-explosive rounds towards the closest capillary tower, which shuddered and groaned under the vicious barrage.

It was a heroic assault that could have been taken directly from the pages of the Codex Astartes, but it would only be a matter of time before the tyranid swarm recovered and surrounded the Fifth’s vulnerable flanks, enveloping the company and preventing any ordered retreat.

Already, Fabian could see the enemy moving to do just that. Led by a towering tyrant-form with a serrated bonesword in each plated fist, a formation of xenos warriors was sweeping around to the south, entering the outskirts of the ruined factory district through which the Third advanced.

The tyrant screeched as it saw the ranks of Ultramarines charging across the rubble towards it. A weapon-organ protruded from its gut, and spat a bolt of sizzling acid that hissed through the air towards Fabian. He veered right, and the projectile smashed into a rubble pile behind him, burning through the shattered stone and sending shards flying through the air to rain off his power armour.

They were only a dozen metres from the tyrant’s force now, and Fabian raised his plasma pistol to fire. It spat a bolt of flame that missed the tyrant by a hand’s width, and burned through the skull of a tyranid warrior behind it. Fabian cursed. How in the Emperor’s name were you meant to hit a thing with these wretched augmetics? Bio-weapon fire spattered off his battleplate in return.

Behind him, perched in whatever elevated positions they could find amongst the shattered and broken towers of the destroyed industrial zone, Devastator squads began to rake the tyranid force with heavy bolter fire and missiles. Smoke trails criss-crossed over Fabian’s head, and he felt the shudder of an impact shock wave run through him as the projectiles detonated, sending up great plumes of churned earth and flesh.

Then Fabian was amongst them, hacking and stabbing with his power sword. The tyrant strode through the storm of fire towards him, smashing aside its fellows disinterestedly as its coal-black eyes bored into him. Fabian blasted a termagant into ash, ducked a swinging claw-scythe and decapitated a screeching monster with a spinning slash. He turned and levelled his blade at the tyrant-form.

‘You wretched creatures took an eye and a limb from me here,’ he said, advancing steadily, wide smile hidden by the mask of his helm. ‘I’ve a mind to return the favour.’

The light rushed back in to Cassius’ eyes, and he struck something hard enough to force the breath from his lungs. For a moment he experienced a disorientation more severe than anything he had felt before, as his brain attempted to sort out up from down, left from right. He was covered in a stringy mucus-like substance, and his vision was blurred.

His mechanical orb picked out a wide, spherical cavern, dark and quiet aside from the steady drip, drip of viscous fluid from a pulsating sphincter set in the wall. He stepped forward, and his boot crunched into something.

At his feet was a tyranid. A genestealer, probably the one he had been grappling with. It lay broken on the floor of the cavern. The lower half of the alien’s torso was a crumpled mess, and its left leg kicked and twitched.

A gruesome injury, and one that gave Cassius some idea of what had just happened. The xenos’ injuries – aside from those he himself had inflicted upon it before he blacked out – were consistent with extreme pressure trauma. Had the Chaplain not been protected by his power armour, he would likely have suffered the same fate.

The chamber throbbed with a peristaltic motion. Cassius stepped back, raising Infernus as the dripping sphincter on the wall bulged. A hulking black shape was vomited forth, and crashed into the Chaplain, knocking him to the floor. He rolled with the impact and came up with Infernus levelled.

He stared into a slime-coated black helm, pockmarked with a hundred battles’ worth of scars, burn marks and dents.

‘Chaplain,’ gasped Sergeant Remas.

The cavern heaved again, and another shape fell to the earth. Apothecary Soemnus dragged himself to his feet, covered in mucus but still clutching the antiviral cylinder.

‘That,’ he said, ‘was a singularly unpleasant experience.’

‘The others,’ said Cassius, ‘where are they?’

‘Kilrian and Pharron fell,’ said Remas. ‘Errath took a bad hit. He stayed to rupture the ingress sphincter after we’d gone through.’

‘You knew what it was?’

‘Not my first time on a tyranid vessel, Chaplain,’ said Remas. ‘It looked different, but when you were dragged through I could take an educated guess.’

The sergeant moved to the membrane door leading out of the chamber, and hacked through it with his power blade. It seeped a foul, milky-white liquid as he carved it apart.

‘We should move,’ he said. ‘Brother Errath has bought us time, but there will be more tyranids converging on this location.’

‘Apothecary, the dosimeter,’ said Cassius. ‘Have we strayed further from our target?’

‘Closer,’ said Soemnus. ‘The pulse is more powerful. I can feel it through the vessel itself – can’t you?’

Cassius could. It was faint, but every few seconds there was a deep, rumbling throb that ran through the chamber in a compression wave of air. The pools of fluid that covered the chamber floor rippled slightly.

‘We’re near,’ said the Apothecary.

‘Then let us hurry, brothers,’ said Cassius.

A vast, dark space opened up before them as they stepped out of the chamber onto a long, narrow walkway formed of twisting sinew. Below was nothing but darkness and empty air, though Cassius could see other sinew bridges stretching across the cavern all around them. Along the ceiling, which was curved and shadowed like that of an immense cathedral, clustered masses of pustule-like growths and trailing masses of fibrous tendrils, flowing in the low gravity as if underwater.

They were half way across when Cassius paused. A cold shiver ran down his spine. Slowly he turned, and looked up and out across the abyss.

It was there, some two hundred metres above him and out across the cavern, crouched on one of the sinew bridges. It was looking right at him.

Its body was softer, dripping with birth fluids and other vile matter, and it was paler than before, but Cassius would remember those the sickening nausea of its psychic presence until the day he died.

‘The Swarmlord,’ whispered Remas, stepping to his side.

‘It lives,’ said Cassius.

How was that possible? He had seen this thing die twice, had seen it left crushed and broken on the ground. And yet still it stood before him. There could be no mistaking it. He felt the old urge again, the need to kill the abomination, to crush it so thoroughly that it could never spread its foul influence across any corner of the galaxy ever again.

The Swarmlord turned away from the veterans and strode across the sinew bridge towards the chamber they had entered from. As it reached the cavern wall, a membrane yawned wide to let it pass. It paused, turned to stare back at Cassius one more time and the Chaplain felt the throbbing in his skull build to a crescendo. Then the repulsive presence drained from his mind, and the creature was gone.

‘We kill it,’ said Remas, starting forward and drawing his combat knife. ‘We can scale that cavern wall. It’s made from soft organics, and the low gravity will help with the weight of our armour.’

‘No,’ said Cassius.

Remas stopped, and turned.

‘What?’

‘No,’ Cassius repeated. ‘Let it go, sergeant.’

‘For Sotha and for my Chapter,’ shouted Remas, smacking the hilt of his power sword against the scarred and pockmarked image of the twin Scythes he wore on his shoulder. ‘You cannot deny me this.’

‘Our duty lies in our mission,’ said Cassius. ‘That mission is clear.’

‘That is not what you said at the fortress,’ retorted Remas. He gestured at Cassius with his power sword. ‘You knew our vengeance meant more than any mission! You ordered us from our posts and you destroyed the Swarmlord!’

‘I know,’ said Cassius. ‘And I was wrong.’

Without another word, the Chaplain made his way across the bridge, away from the Swarmlord. Apothecary Soemnus followed. After many moments, so did Sergeant Remas.

The second capillary tower fell. The Fifth Company held off the increasing numbers of tyranids long enough for the Vindicator tanks Proethus, Vengeance of Calth and Dominus to launch a sustained barrage. Their demolisher cannons fired, loud enough to burst eardrums. Detonations rippled along the base of the tower. Proethus scored a direct hit on the centre of the structure, sending a storm of chitin shards scything through the tyranid swarm, slicing in half those creatures not instantly incinerated by the force of the detonating explosives. The rest of the tower fell in segments, each crushing scores of swarming tyranids as it crashed to earth.

A cheer went down the Ultramarines’ line, only to be cut off as a counter-barrage from tyranid artillery beasts lurking behind the main enemy force struck home. Bio-plasmic rounds seared through the thick armour of Dominus, rocking the venerable tank on its tracks. A second barrage struck the breach that the first had created, and the Vindicator’s ammunition bay went up. The detonation was incredible. A mushroom cloud of flame and dirt split the tank apart, and sent the wreckage of the Dominus crashing into the Proethus. A vicious shock wave sent the closest Ultramarines battle-brothers sprawling, and the concussive force ruptured the brains of the weaker tyranid organisms, dropping dozens of them where they stood.

‘We’re pushing through to the third tower, Galenus,’ Fabian voxed to his fellow captain, shouting over the ringing in his ears. ‘Sweep around to the northern digestion pool.’

The combined attack of the Third and Fifth had brought down two of the alien towers and targeted the southern digestion pool so thoroughly with artillery and heavy weapons fire that most of the foul liquid within had been super-heated and evaporated, leaving little more than a brown-grey morass behind. Fabian saw tyranids mired in the swamp of broken-down organic matter, struggling weakly, unable to pull free.

But ten towers still remained, and the tyranids brought more and more of their foul xenoforms to the field with every passing moment.

‘Come on, Chaplain,’ whispered Fabian. ‘Give us something.’

‘Captain!’ came a shout from behind him. He turned, and saw Sergeant Vorrel gesturing to the south-eastern edge of the battle.

A phalanx of bipedal tyranid warriors sliced into the Third Company’s right flank, taller than the swarm-creatures, and armed with boneswords and heavy weapon-organs that vomited forth storms of living projectiles. Fabian saw brothers fall, and cursed as the tyranid warriors charged into the gaps in the line, laying about them with their vile blades.

Cassius grabbed the tyranid warrior’s chitin blade, ignoring the pain as its monomolecular edge cut into the flesh of his palm, and crushed the creature’s skull with an overhead swing of his crozius. Behind him he heard the roar of Remas’ bolt pistol, and the grinding, tearing sound as Apothecary Soemnus sunk his chainsword into enemy flesh.

They had pushed even further into the depths of the ship, and now the regular pulse of energy was a punch to the base of the skull that disoriented and sickened. Cassius felt blood trickling from his eyes and nose. They could not stay here for long. Even their transhuman resilience was little defence against the devastating power that gave this foul vessel life.

‘Ahead,’ gasped Soemnus, swaying as he staggered forward. They were in a cylindrical hallway comprised of hundreds upon hundreds of thick, muscled tubes that pulsed and surged. Remas knelt at the entrance, power sword stabbed into the floor, reloading his bolter with trembling hands.

‘Go,’ he said, and Cassius could hear the blood filling his mouth. ‘I will hold here.’

Soemnus and Cassius made it, step by step, to the end of the hall. Soemnus swept his chainsword through another wall membrane. Beyond was a vast mass of dark red muscle, a bundle of looping sinew and ribbed, fleshy tubing taller than two Space Marines. It was topped with a glowing blue crystal that burned with an unnatural light so fierce it hurt Cassius’ eyes to look upon, enveloped in a thick mass of spongy neural tissue, wrapped and entwined like deep-sea coral. Above them, soaring through the darkness, was an enormous branching mass of arteries and veins that would pump oceans of ichor through the hive ship with every deafening throb of the heart.

It pulsed again.

Cassius staggered and gasped, hit with a shock wave of unimaginable force. It shook his bones, grabbed his brain and crushed with the force of a power fist. He teetered and felt himself swaying. He coughed blood.

Soemnus was face down in the damp floor of the cortex chamber. The cylinder containing the antiviral rolled free from his limp hand.

Cassius tried to stand, could not, and fell back on his hands and knees. The world swayed around him. He was dimly aware that there was something he needed to do. The antiviral.

He crawled forward, grabbed the cylinder, and with a surge of furious defiance, he hauled his battered body upright. He took a step forwards, then another, stepping over the prone form of the apothecary. He heard the hideous wails of the xenos in the distance, interspersed with the bark of a bolt pistol. The pistol fell silent, and Cassius felt his fury rising. No more brothers would die at Kolovan. He hacked into the muscle of the energy cortex and discharged the power field of his crozius and the toughened flesh splattered across his amour.

He could have struck his blow in the name of Macragge, of all their fallen, of the dead of Kolovan or all those who had fallen prey to the Kraken. But the scale of the tyranids’ crimes against the Imperium was too vast for mere words. So Cassius said nothing as he rammed his fist into the muscle of the organ, felt it reach into an open chamber beneath, and released the antiviral into the heart of the hive ship.

Galenus rolled with the impact of the strike, splashing through a rivulet of foul biomatter. The stench of the vile fluid filled his nostrils. He rose, slashed an onrushing creature to the ground, reversed his grip and drove his blade through its back. The hive tyrant came forward again, swiping its heavy talon across so fast that the captain could not bring his blade up to block.

Ceramite sheared, and Galenus was thrown backwards. Armour-breach warning runes flashed across his helm, and the breath was torn from his chest. The tyrant came forwards, and brought its right talon back for another slash. There was a blur of blue and gold armour, a sharp crack, and the creature’s arm flew free. Captain Fabian barrelled in, power sword hacking and carving. It tried to dodge the furious assault, fending off the vicious sword with its remaining limb.

Galenus staggered to his feet, ignoring the agony in his chest, and drove his own blade deep into the creature’s thigh. It arched its back and screeched, sinking to its haunches. Fabian took his blade in two hands and sliced through the tyrant’s mouth. The top of the skull fell free with a spurt of grey-white fluid.

‘My thanks, brother,’ gasped Galenus, as Fabian put an arm around his back, holding him upright.

‘Don’t thank me too soon,’ Fabian said. His voice was grim, and as Galenus surveyed the battle, he saw why. The tyranids had flanked the Third, pushing them back until they formed an island of blue armour with the Fifth. Several tanks had been reduced to smoking wrecks, and the enemy was already swirling around to envelop the Ultramarines’ position entirely. Flying organisms hurled acid and bio-chemical rounds into the packed ranks of Space Marines, who now had no chance at all of reaching the remaining feeding towers. It was over.

‘This is it, then, brother,’ said Galenus. ‘Let us take as many of these wretched creatures with us as possible.’

‘The Third and Fifth side by side until the end,’ said Fabian, checking the charge of his plasma pistol. ‘How fitting.’

Galenus drew his combi-melta. Ahead of the two captains, the mass of the enemy swarm was hurled aside as something bulldozed its way through. With a deafening roar, three enormous siege-beasts crushed their way towards the Ultramarines, talons sweeping both tyranids and Space Marines aside. Fabian and Galenus raised their weapons to fire.

They never did. Only a few metres away, the three siege-beasts staggered, suddenly off-balance. The momentum of their charge sent the leading beast sprawling, digging up a channel of earth as its colossal weight scraped across the churned ground. It wailed, a bizarre sound coming from such a hulking, monstrous creature, and thrashed its talons. The other two beasts pulled up short, as if entirely unaware of their surroundings.

Galenus and Fabian did not stop to wonder at their good fortune. They rushed to the fallen siege-beast, driving their power swords deep into its skull, again and again until it fell still. The other two creatures roared, and began to slice at the nearest object they could lay their eyes upon. One started hacking and tearing at the smoking ruin of a Predator tank, pounding and beating at the inanimate metal. The other turned on its own kind, carving a path through the swarming hormagaunts.

‘What in the name of the primarch is going on?’ asked Fabian.

Galenus looked around. Only moments before, the tyranids had been pressing them mercilessly on all sides. Now the creatures milled, uncertain and distracted. Some still fought, but others turned back into their own ranks, or stood, dazed, as the Ultramarines’ weapons cut into their flesh.

‘The Chaplain!’ said Galenus. ‘He must have deployed the antiviral.’

‘It doesn’t matter what has happened,’ said Fabian. ‘This is our chance! All squads forward, now, assault formation. This is the moment, brothers! This is the hour of Kolovan’s vengeance! Forward to victory!’

Roaring battle-hymns and oaths of vengeance against their hated enemy, the Ultramarines of the Third and Fifth Companies tore into the disorganised tyranid ranks.

Epilogue

Victory came too late to save Kolovan.

That was a harsh truth that every Ultramarine had understood from the moment they set foot on the planet’s surface. There would be no grateful, smiling refugees to thank them for the blood spilt in its defence, and there would be no slow recovery, no healing, no triumphant return to the Imperial fold.

Kolovan was a dead world. Ninety-three per cent of the planet’s industrial infrastructure had been destroyed beyond repair, and the climactic torture that the xenos spore seeding had unleashed across the world had filled the atmosphere with toxic gases that even the colossal filtration plants could not eradicate. A single breath would be enough to dissolve the lungs of a man. Rehabilitation was out of the question.

The death of a planet was not an uncommon occurence in the 41st millennium. As it died, Kolovan at least provided hope that other worlds could avoid a similar fate.

As the antiviral devoured the hive ship from the inside, spreading through its twisted chambers, breaking down vital organs and drowning the vessel in a tide of its own foetid life-fluids, the tyranid force that guarded the digestion pits had been denied the synaptic guidance that linked and co-ordinated their movements. The combined force of the Third and Fifth Companies, with Captains Galenus and Fabian at the fore, counter-charged the tyranid advance and swept the enemy from the field. There were still countless thousands left alive to watch the hive ship descend into the upper atmosphere, like a vast cephalopod plunging through the depths of the ocean. Its dead, grey flesh sloughed off its sides as the friction of the descent tore it free. Bones and dead organs, freeze-dried by the void, came away as the hive ship disintegrated.

The flesh of the gargantuan hive ship rained down across Kolovan. By the time it hit the surface of the ocean there were only bones left – the rest of it was drifting in the planet’s prevailing winds, darkening the acidic sun and bringing a new and unforgiving winter. There would be bloody fighting in the subsequent months, as the tyranid threat was hunted down and terminated xenoform by xenoform, but with the mother-ship gone and the digestion pools and capillary towers of Adverica destroyed, the remaining tyranid fleet could not gather enough biomass to fuel their advance across the segmentum.

The loss of the world meant little beyond the Kolovan system. The Adeptus Mechanicus stronghold of Ryza was embroiled in its own wars and the other planets of the sector were concerned primarily with ensuring that repeated greenskin incursions did not darken their own horizons. A brief summation of the fall of Kolovan would be added to the records, but its true importance would largely be forgotten. Billions of Imperial citizens would live on, oblivious, never knowing just how close they had come to obliteration.

Cassius would write of what truly happened. He would describe how the fall of Ryza and of the Segmentum Solar’s defences had been averted, and of the martyrdom of Kolovan. Of the Adeptus Mechanicus scientists, too, and all the Ultramarines who had fallen on the surface of Kolovan and above it.

‘Though the Imperium may stay ignorant,’ said Cassius, ‘we will know. We will teach it.’

He spoke to the bodies of scores of dead brothers, which lay on mortuary slabs in the apothecarion of the Defence of Talassar. In the calm between warp jumps the old ship was silent, its engines and reactors powered down for maintenance, and the apothecarion was as cold and still as death. Almost half of the Fifth Company had been lost, and the Third had suffered similarly. Such sacrifice demanded remembrance.

‘A costly victory,’ said Remas, ‘especially for a dead world.’

‘It was,’ said Cassius. ‘Many brothers fought their last battle here, and many progenoid glands went unreclaimed. But Apothecary Dionys extracted the majority. The Third and Fifth Companies will march again.’ Cassius looked up at the Sergeant. ‘But the Scythes of the Emperor will not. That is what weighs on your mind.’

‘It matters little,’ said Remas. ‘Our duty was done. Our mission was fulfilled.’

‘You wish you had died alongside these warriors,’ said Cassius, gesturing at the bodies laid out on the slabs. ‘The fates of the galaxy have not given you that luxury. Envy the dead if you will, Sergeant Remas, but the Emperor is not done with you yet.’

After deploying the antiviral, Cassius had hauled the unconscious Soemnus out of the energy cortex chamber, and had found Remas lying amongst a pile of tyranid corpses, bolt casings scattered on the floor around him. Together, the three survivors had dragged themselves to one of the dying ship’s dorsal valves, and Cassius had activated his distress beacon. There they had waited, exhausted and bleeding from countless wounds, waiting for salvation and watching the ship decay and break apart around them. Finally, transport shuttles from the Defence of Talassar had located them. Remas had been adamant that they return into the depths of the ship for the remains of his squad, but Cassius had denied him. The ship was listing into the upper atmosphere, and they had no time to delve through the vessel’s halls.

‘I have known the rage that fills you,’ said Cassius. ‘Both of us have known loss beyond measure. I have defended this Imperium of Man for centuries, and in that time I have charged into battles I had no hope of winning, all for the sake of vengeance.’

‘You are still here,’ said Remas. ‘You have lived a long time for a reckless man.’

‘I am not foolish enough to think my fortune will last forever,’ said Cassius. ‘Both of us will die serving the Emperor. That is our birthright, and our duty. But there is no honour in a vain death, earned in pursuit of selfish goals. You honour the fallen Scythes by living, and by finding a way to punish the tyranids for what they have done. We did that on the hive ship, you and I. We will find the chance to do so again.’

‘Perhaps you are right, Chaplain. Perhaps the last Scythe of the Emperor can one day avenge his Chapter,’ said Remas. There was the ghost of a smile on the Scythe’s face. ‘I have duties in the sparring chamber. Gerion wants to try to twist my head off.’

‘Then I should not hold you,’ said Cassius. ‘And I have duties of my own here.’

Cassius moved among the dead, recognising each face and recalling the deeds and memories that once spurred them on to fury or restraint. He added their names to the long list of the fallen he had filed away in the most sacred part of his memory. Then he knelt on the cold steel apothecarion deck, and began to pray.

About the Author

Ben Counter is one of Black Library’s most popular Warhammer 40,000 authors, with two Horus Heresy novels to his name – Galaxy in Flames and Battle for the Abyss. He is the author of the Soul Drinkers series and The Grey Knights Omnibus. For Space Marine Battles he has written the World Engine and Malodrax, and has turned his attention to the Space Wolves with the novella Arjac Rockfist: Anvil of Fenris and a number of short stories. He is a fanatical painter of miniatures, a pursuit which has won him his most prized possession: a prestigious Golden Demon award. He lives in Portsmouth, England.

A Black Library Publication

First published in Great Britain in 2016
This eBook edition published in 2016 by Black Library, Games Workshop Ltd,
Willow Road, Nottingham, NG7 2WS, UK.

Produced by Games Workshop in Nottingham.
Cover illustration by Mac Smith.

Cassius © Copyright Games Workshop Limited 2016. Cassius, GW, Games Workshop, Black Library, The Horus Heresy, The Horus Heresy Eye logo, Space Marine, 40K, Warhammer, Warhammer 40,000, the ‘Aquila’ Double-headed Eagle logo, and all associated logos, illustrations, images, names, creatures, races, vehicles, locations, weapons, characters, and the distinctive likenesses thereof, are either ® or TM, and/or © Games Workshop Limited, variably registered around the world.
All Rights Reserved.

A CIP record for this book is available from the British Library.

ISBN: 978-1-78572-459-6

This is a work of fiction. All the characters and events portrayed in this book are fictional, and any resemblance to real people or incidents is purely coincidental.