'They're coming through the walls,' said Aneis. Humanoid and other shapes were coalescing through the bare plasteel bulkheads around the Navigators; too many to destroy.

'Pick up your brother,' Fiana told Coiden. She grabbed Aneis by the shoulder and dragged her brother past the pair. She gave him a shove towards the door leading through the next bulkhead. Something pot-bellied and cyclopean was forming out of a dark pool of rust and slime spreading across the floor of the passage beyond.

'Clear a path,' Fiana said.

'Where to?' Aneis asked, his youthful face almost white with fear.

'The strategium,' replied Fiana. 'We must reach the protection of the Lion.'

Having recovered some of his equilibrium, Corswain did all that he could to organise a defence of the gun decks, but the mysterious invaders were all but impossible to confront. From the scattered outbreaks across the Invincible Reason, it was clear that the attack was not confined to the gun batteries, or even the starboard decks. Pockets of foes were appearing across the vessel, with a large number seemingly intent on taking over the warp core chamber. With foes materialising behind defensive lines, making a mockery of any physical barrier that could be erected, Corswain had mobilised the ship's company into hundred-strong patrols.

Not far from the strategium, he and his bodyguard came across Lady Fiana and her family. They were being escorted by Sergeant Ammael and his squad and though the Navigators looked distraught and haggard none of them seemed to be seriously injured. The seneschal relieved Ammael of his obligation and sent him to the engine decks where the fighting was becoming protracted.

When the group reached the strategium, they were confronted by an unexpected sight. There were no signs of fighting here; the technicians went about their duties with crisp calmness, diligently ignoring the scene that was playing out in their midst.

The Lion stood at the centre of the main chamber, and before him knelt a Dark Angel, a white tabard over his black armour, head bowed in obeisance. Surrounded by his personal guard, Brother-Redemptor Nemiel stood over the kneeling legionary, his pistol and crozius in his hands.

'Wait here,' Corswain quietly told the Navigators, motioning for them to stand to one side. The Lion heard the whispered words and looked across at Corswain.

'Your timing is unintentionally impeccable, little brother,' said the primarch. 'I am faced with a dilemma.'

'My liege, I do not know what is happening here, but I am sure it can wait a while. We need your guidance. The ship is under sustained attack, from creatures that are almost impervious to our weapons.'

'The punishment of oath-breakers brooks no delay,' said Nemiel. As he approached, Corswain recognised the kneeling legionary. His helm was under his arm, his face half-hidden behind long waves of black hair. It was Brother Asmodeus, formerly of the Librarium.

'Oath-breaker?' said Corswain. 'I do not understand.'

'My little brother has transgressed,' said the Lion, though there seemed no anger in his voice. 'Upon being attacked, he broke the Edict of Nikaea and unleashed the powers of his mind.'

'He performed sorcery,' snarled Nemiel. 'The same vileness perpetrated by the Night Lords that now threatens our ship!'

'That is to be decided, Brother-Redemptor,' said the Lion. 'I have not yet delivered my verdict.'

'The Edict of Nikaea was absolute, my liege,' said Nemiel. 'Warriors of the Librarium were to curtail their powers. Asmodeus has breached the oath he swore.'

'Did it work?' said Corswain.

'What?' said Nemiel, turning his skull-faced helm in the direction of the seneschal.

'Asmodeus, did your powers destroy the enemy?'

The former Librarian said nothing, but looked up at the primarch and nodded.

'Interesting,' said the primarch, his green eyes fixing on Corswain as if to see into his thoughts.

'I have seen first-hand what these things can do. They are...' said the seneschal, hesitating to use the word. He took a breath and continued. 'We face nephilla, my liege, or something akin to them. They are not wholly physical and our weapons do little damage to their unnatural flesh.'

'They are creatures of the warp, lauded primarch.' The group of Dark Angels turned as Lady Fiana approached. 'They are made of warp-stuff, and the breach has allowed them to manifest in our world. They cannot be destroyed, only sent back. The gaze of our third eyes can harm them.'

'Is this true?' asked the Lion, stooping to lay a hand on the shoulder of Asmodeus. 'Were your powers capable of harming our attackers?'

'From the warp they come, and with the power of the warp they can be banished again,' said the Librarian. He stood as the Lion changed his grip and guided the legionary to his feet. He met the primarch's gaze for a moment and then looked away again. 'Brother-Redemptor Nemiel is right, my liege. I have broken the oath I swore.'

'A grave crime, and one that I will be sure to prosecute properly when the current situation has been resolved,' said the Lion. He looked at Nemiel. 'There are two others of the Librarium aboard: Hasfael and Alberein. Bring them here.'

'This is a mistake, my liege,' said Nemiel, shaking his head. 'The abominations that attack us, these nephilla, are a conjuration of sorceries. I swore an oath also, to uphold the Edict of Nikaea. To unleash further sorcery will endanger us even more. Think again, my liege!'

'I have issued an order, Brother-Redemptor,' said the Lion, drawing himself up to his full height.

'One that I cannot follow,' said Nemiel, his tone hard, though Corswain could see the Chaplain's hands were trembling with the effort of defying his primarch.

'My authority is absolute,' the Lion said, clenching his fists, his lips drawn back to reveal gleaming teeth.

'The Edict of Nikaea was issued by the Emperor, my liege,' said Nemiel. 'There is no higher authority.'

'Enough!' The Lion's roar was so loud it caused Corswain's auto-senses to dampen his hearing, as they would if he was caught in a potentially deafening detonation.

The seneschal was not entirely sure what happened next. The Lion moved and a split-second later a cracked skull-faced helm was spinning through the dull-glowing lights of the strategium, cutting a bloody arc through the air. Nemiel's headless corpse clattered to the floor as the Lion held up his hand, pieces of ceramite embedded in the fingertips of his gore-spattered gauntlet.

Corswain looked at the face of his primarch, horrified by what had happened. For a moment he saw a vision of satisfaction, the Lion's eyes gleaming as he stared at his handiwork. It passed in a second. The Lion seemed to realise what he had done and his face twisted with pain as he knelt beside the remains of the Brother-Redemptor.

'My liege?' Corswain was not sure what to say, but as seneschal he knew he had to act.

'We will mourn him later,' said the Lion. The primarch stood up, his gaze still on Nemiel's body. He broke his stare and looked at Lady Fiana, who flinched as if struck. There were three droplets of blood across the pale flesh of her right cheek. 'Tell the Librarians they are relieved of their Nikaean oaths. Lady Fiana, you and your family will each lead a company of my warriors. Cor, assemble eight counter-attack forces.'

'Eight, my liege? Three for the Librarians, and one each for the Navigators, I understand. Am I to lead the other?'

'I am,' said the Lion. 'No creature, nephilla or any other, attacks my ship without retribution.'

V.

While his seneschal organised the forces of the Dark Angels, the Lion made his way to his personal arming chamber. Five Legion serfs were awaiting him inside the stone-clad room, dressed in dark green surplices, with heavy boots and gloves. Each wore a pistol at his belt too, though the Lion had encountered no enemy on his way there and they appeared unmolested.

The reports of attacks were growing in frequency as the nephilla or whatever their immaterial assailants were seemed to be widening the breach from warp space to allow more of their kind to manifest.

The walls of the chamber were covered with weapons of dazzling variety, either made for the primarch or seized as spoils of conquest from the hundreds of cultures he had encountered during the Great Crusade. It had begun with his first Calibanite short sword, presented to him by Luther on acceptance into the knightly order; that simple blade held pride of place at the centre of the display.

It was the one affectation he allowed himself, this collection of weaponry. He had spent long times here contemplating the many ways mankind had devised to kill an enemy, though of late his throne chamber had been a more regular haunt. He paused for a moment of thought, moving along the walls, touching a hand to favourite pieces, running a gauntleted finger along blades and spikes in appreciation of their craftsmanship. In war, just as in other pursuits, mankind was creative, showing insight and genius even with the most barbaric level of technology.

Many of the weapons were too small for his fist and were mounted for ornamentation only, while others served a different purpose in his hands: swords for normal men wielded as knives by the Lion. Some were traditional, ancient designs, while others had monomolecular edges, power field generators, electro-fields and other technological improvements.

There were spatha, longswords, bastard swords, mortuary swords, flambards, rapiers, sabres, scimitars, khopeshes, colichmardes, tulwars, shotels, falchions, misericordes and cutlasses; myrmex, cestus and knuckle dusters; baselards, stilettos, dirks and daggers; cleavers, sickles and kopis; mattocks, clubs, picks, maces, flails, morning stars, mauls and war hammers; hatchets, tomahawks, hand axes, double-bladed axes, long-bearded axes and adzes; pikes, partisans, fauchards, sarissas, voulges, Lochaber axes, boarspears, tridents, halberds, scythes, half pikes and hastas.

He did not rush himself, but took the time to collect his thoughts, considering the enemy of the day. In his youth he had slain nephilla with his bare hands out of necessity, though they were all but impervious to most mortal weapons; another benefit of his primarch heritage. This day he would go armed, and he took up two blades, heavy hand-and-a-half broadswords by the reckoning of normal men but easily held in each fist by the giant primarch. They were superbly crafted, the product of a Calibanite artisan whose name had been lost to history. Their names were inscribed along the edge of each blade in florid lettering: Hope and Despair. Each had a long fuller to lighten the blade weight, and they were edged with a crystalline compound sharper than any metal, unbreakable and never needing to be sharpened. The Lion had found the pair of swords used as ceremonial pieces by one of the order masters, and becoming enchanted by their glittering edges had insisted on a trade, gaining them for the exchange of an unblemished sablesabre pelt the primarch had prepared by his own hand.

Armed with the twin blades, the Lion joined his allotted company at the main gateway above the reactor rooms and warp core, where the fighting was fiercest. Several wounded legionaries were being dragged up the access ramp, suffering a variety of horrendous wounds: burns and slashes through their armour that had gouged down to the bone.

'Fight with pride, die with honour,' said the Lion, raising his swords in salute to his little brothers. They fell in behind their primarch, forming five lines each fifty strong.

The corridors were littered with the dead; unarmoured serfs and crew for the most part. Their ragged bodies were heaped in bloody piles and choked the doorways to side chambers. Some had heads or limbs missing, others were little more than blackened lumps of charred flesh. Some were arranged in lewd poses with each other, eliciting a growl of disgust from the primarch.

Here and there, flies and maggots were already crawling through the filth of the dead, burrowing beneath the skin of the fallen and feasting on lifeless eyes. The Lion heard muttered curses uttered by his company, but had no desire to silence them, for he felt like cursing also.

He stopped as he came across the form of two dead Dark Angels. He knelt beside them. Their armour was half-melted as if by acid, and their skin was pock-marked by blisters and buboes. Caliban had occasionally been wracked by strange plagues, and the clusters of triple pustules that corrupted the skin of the pair of dead Space Marines struck a chord in the memory of the Lion.

'We have to burn the dead, lest corruption spread,' he said solemnly as he straightened. A trail of slime, like that of a snail, only a metre wide, led away from the bodies and passed into one of the passages leading away from the main corridor. The primarch detailed a squad to hunt down the creature that had left the trail and pressed on towards the main engine rooms several hundred metres ahead.

From nowhere, eight nephilla sprang into being ahead of the primarch. The warp rift had become so strong that it took almost no time at all for the attackers to materialise. These creatures were vaguely humanoid in shape, with lean, hunched bodies and wiry arms. They had legs like those of a dog and their flesh was the colour of blood and faintly scaled. Their heads were elongated, with black horns running back along the sides. In clawed hands they held triangular swords of gleaming bronze. Eyes of pure white regarded the Lion for a moment while forked tongues licked needle-like teeth.

With snarling war cries the nephilla attacked as one, raising their swords as they rushed towards the Lion. He did not wait for the enemy to come to him, but sprang forwards to meet them. In his left hand, Hope parried two blades swinging towards his groin, while Despair hacked through the neck of one of the creatures, parting the immaterial tissue of its body without pause.

The Lion felt a shock of energy ripple through him from his hand as the creature exploded into a shower of blood, coating the floor and the Lion's armour with crimson. There was no pause to marvel at this strange death, for the remaining seven creatures were trying to encircle the primarch.

Bolt shells whined and cracked as the other Dark Angels did their best to help their commander. The detonations had little effect on the nephilla, but provided distraction. Sweeping Hope in a wide arc, the Lion sheared through an upraised blade and parted the bodies of two more attackers even as he stabbed Despair through the face of another. The blades of the nephilla bit at his black-and-gold armour, cutting deep into the enamelled plates in a way no mortal weapon had ever done, though the Lion's flesh remained unmarked.

Parrying another swing of an infernal blade, the Lion twisted and brought Despair down onto the head of a nephilla circling behind him, cleaving through black horn and red skin. There was no skull beneath the flesh, and the creature collapsed into a crimson pool like the others. In two more seconds and a flurry of blows, the Lion had despatched the rest of his assailants, and his armour was awash with sticky red fluid. It smelt like blood, but he knew it could not be; the creatures had possessed no veins or arteries or hearts to carry such a thing.

Perturbed by this discovery, the Lion continued on, calling for his guard to follow swiftly as he splashed through the slick of red. He signalled Stenius, who had remained in the strategium.

'How long until the warp drive is operational, captain?'

'Less than twenty minutes, my liege,' came the reply after a few seconds. 'We have a problem, though. The enemy have driven the engineers from the warp core and are attempting to break into the containment chamber. Lord Corswain and Lady Fiana are trying to break through from the aft decks, my liege.'

'I will meet them in the main core chamber, captain.' The Lion broke into a run, his long strides quickly leaving behind his company of Dark Angels.

Corswain felt only a little better that he had Lady Fiana for company. The gaze of her third eye was devastating to the enemy, but she tired quickly and had to rest for several minutes between bursts. For those periods, it was up to him and the other Dark Angels to protect her with their mundane weapons. It was not impossible the nephilla could be destroyed by weight of fire or a particularly powerful blast of a lascannon or such but it was hard work and the force was expending ammunition and power packs at a prodigious rate. They had less than half the stores they had set out with by the time they reached the conveyors and stairwells that dropped down into the warp core chambers.

They had encountered all manner of horrifying foes on the two-kilometre journey aftwards: soaring disc-like beasts ringed with razor-sharp claws and possessing mouths that could chew through a legionary's armour in a few seconds, six-limbed entities with giant lobster claws and lashing tongues coated with venom, ever-changing apparitions with leering faces in their torsos that cavorted and wheeled about whilst spitting sorcerous fire from their fingertips.

Corswain's original force of two hundred Dark Angels now numbered just over half that; twenty-eight had been slain or were in the apothecarion, the others had been left as rearguard to defend against the enemy who could materialise anywhere.

With his personal guard close by him, the seneschal descended the main stairway into the bowels of the engine decks while other squads split to clear out secondary access routes. The steps were littered with the bodies of dead crew. Amongst the decapitated and disembowelled corpses were a few legionaries, their black armour rent open, their flesh hideously corrupted and twisted. Corswain had no idea what could have caused such horrendous injuries, and agitation caused him to tighten his grip on his bolt pistol and power sword as they reached the deck below.

All was clear, save for the stench of death coming from the bloated corpses of engineers and serfs. The passages here were lined with power conduits, piping and cables, which all showed signs of decay and disrepair, marked by patches of corrosion and slicks of moss and algae. Knowing that Stenius would never allow such a poor state to exist on his ship, Corswain was forced to conclude that the decrepitude was somehow a side effect of the nephilla's presence.

The same was true on the next level down, and still no foe could be found. Meeting up with sixty of his Dark Angels, Corswain readied himself for the descent to the warp core deck. The corridor and stairwells thrummed with energy, but not just the power of the reactor that was being fed into the area; there was a tension in the air, an intangible shadow that clouded his thoughts.

'The warp presence is almost total here,' warned Fiana. Her face was screwed up with effort, sweat running down her brow and cheeks, her lip trembling. 'If it were not for the lack of alarms, I would think the warp core had been breached.'

'Everybody stay alert,' Corswain told his warriors; somewhat unnecessarily he realised, as everybody was on edge. 'No friendlies. Destroy everything that moves.'

He led the force down into the warp core sector. The walls were plated here, thick ferrocrete layered with adamantium. In layout, the deck was oval, a main corridor running around the core room itself, with branching passageways leading to monitoring stations and watch rooms.

The dead were everywhere, some of them so horrendously mutilated that it was hard to tell that they had once been men and women. In the first hundred metres, Corswain counted seven dead Dark Angels, two of them in the livery of Techmarines. The first door to the warp core was another hundred and fifty metres ahead and the piles of the deceased grew larger the closer they came to the gate.

Gunfire sounded from behind, and at the same time a wave of nephilla poured from the doorway leading to the main core chamber. They were of a type, all small creatures with faces in their chests, their unnatural flesh a glowing pink colour. Sparks and trickles of fire dripped from the open ends of their splayed fingers as they gambolled and cartwheeled along the corridor.

The Dark Angels opened fire, a hail of bolts meeting the nephilla fifty metres away. Corswain fired his pistol repeatedly, directing his shots against the same target until finally the creature ruptured, clouds of pink mist erupting from the wounds. Rather than fall, the nephilla started to shudder and spin crazily, a juddering shriek emitted from its lipless mouth.

Corswain stopped firing, shocked by what happened next.

The pink nephilla was mutating, growing an extra head, splitting into two other forms. Its pinkness turned purple and then into a deep blue as two smaller versions of its former shape snapped into existence with an audible popping noise. The blue creatures snarled and frowned at their attackers, fingers flexing menacingly. The same was happening to others, turning the pink tide into a wash of pink and blue as other nephilla were torn apart by gunfire only to re-emerge in their newer forms.

Firing on semi-automatic, Corswain plunged forwards, sword raised. He was just a few strides from the front of the blue mass when a black beam seared past him; the third eye of Lady Fiana. It tore a gouge through the mass of nephilla squeezed into the passageway, causing their bodies to disperse into blue and pink sparks where it touched them.

His pistol empty, Corswain swung his sword at the closest enemy, the power-field-edged blade hitting the outstretched arm of the creature. The impact felt strange, not at all like the slowing of a sword cutting into flesh, nor like the sudden jar of a strike against armour; it felt as though Corswain struck some fantastic rubber that bent under the strength of the blow before rebounding into its former shape.

Fiana's third eye blazed again, opening up a gap for the Dark Angels to plunge forwards into the midst of the foe, their bolters roaring, the sergeants' chain-swords whirring and power fists crackling. Fire engulfed them, purple and red, crackling along the edges of their armour, seeping into the cracks and joins. Corswain's right greave was set alight, the paint peeling away to reveal the ceramite beneath, which started to slough away. As he chopped his sword into the leering face of a nephilla, he noticed in a detached way that the flame gave off no smoke, and that unsettled him even more than the fact that his leg was on fire.

The edge of the pelt hanging down his back caught fire, but before the flames spread, they dissipated, vanishing as swiftly as they had materialised. Turning his attention back to the enemy, he realised that they had all been destroyed. A multicoloured mist hung in the air, like droplets of dye in a zero-gravity environment.

As he reloaded his pistol, Corswain signalled his primarch on the direct command channel.

'My liege, we are about to enter the main core chamber,' he reported. 'How close are you?'

'Two decks down, little brother.' The Lion's voice betrayed no strain, though his next words were a testament to the ferocity of the opposition ranged against him. Corswain could hear feral howling and inhuman shrieking in the background, much of it cut abruptly short. 'I am facing several dozen enemies at the moment. It will take me some time to slay them all. My force is moving up, about three hundred metres behind me. Secure the core chamber and I will meet you there shortly.'

Acknowledging his primarch's reply, Corswain reloaded his pistol and gathered his warriors seven fewer after the latest encounter and headed towards the gateway to the core chamber. The gate itself was several metres high, the blast doors that had been brought down still in place but torn and melted through, leaving a hole large enough to step through.

Corswain expected the portal to be held against them, but no nephilla opposed the Dark Angels as they entered the portalway. High pitched shrieking and wailing sounded from the main chamber beyond, a sound impossible for humans to make. Stepping through the breached barrier, weapons at the ready, Corswain moved into the hall housing the warp core.

The core itself was in a heavily shielded octagonal structure at the centre of the high-domed chamber, enclosed by layer after layer of protective sheaths. Mechanicum symbols were etched into the housing, forming an intricate web of lines and shapes filled with gleaming metal against the obsidian-like stone of the warp core.

Dozens of nephilla the pink and blue creatures they had just fought were frenziedly hurling themselves at the core, clawing at it with their hands, trying to burn their way through with jets of pink flame. Their screeches were utterances of rage and frustration. Other creatures swirled about the upper gantries surrounding the core, swooping and climbing like Gadian skysharks. The nephilla paid the Dark Angels no heed as they strode into the chamber, weapons levelled, intent as they were on breaching the warp core.

'Destroy them all!' barked Corswain, opening fire with his pistol.

The fusillade of the Dark Angels bolters, heavy bolters, lascannons and missiles ripped into the mass of creatures gathered around the core structure. Spreading out along the walkways, the legionaries kept up the murderous rain of fire, some turning their weapons towards the ceiling as the circling beasts above dived down with piercing screams, their tails lashing, the barbs and serrations that ringed their manta-like bodies undulating as they descended.

The chamber filled with a swirling miasma of dissipating energy as the Dark Angels let fly with their fury, billowing clouds of warp power streaming upwards. Through the mist, Corswain saw something else moving, coalescing from the floating fragments that drifted up like embers from a fire. Something larger than anything he had yet seen, towering above the Space Marines, even taller than the Lion yet not so bulky.

Red lightning flared from the mist, ripping through Sergeant Lennian's squad, cracking open armour and searing flesh in a long burst of raging energy. Their smoking bodies were flung through the air by the blast, smashing high up against the ferrocrete walls.

The thing that emerged from the swirling maelstrom of dying nephilla looked like a giant, nightmarish bird, at least four metres tall. It stood upright like a man, but its thin, twisted body was supported on legs like those of a hawk or eagle, taloned feet scarring the metal floor, leaving sparks in its wake as it advanced. Robes of fire hung from its torso, blown about by some unnatural wind. Its arms were long and sinewy, and in its clawed hands the creature held a staff made of solidified flame, ever-changing in colour. A pair of wings spread from the beast's back, almost reaching from one side of the chamber to the other, iridescent feathers trailing on the ground.

It had two heads on long scaled necks, one like some grotesque vulture, the other serpentine, both crested with long multi-coloured feathers that dripped red and blue droplets of fire. And its eyes... Corswain regretted meeting that abominable gaze in an instant, but was unable to look away. The nephilla's eyes were black: the black of the gulf between stars, the black of the darkest cave of Caliban. The seneschal saw himself reflected in those ebon orbs, a tiny figure against the huge expanse of the universe a tiny, insignificant mote surrounded by the enormity of existence.

The nephilla lashed out with the tip of its staff and more lightning filled the chamber, ripping apart another half a dozen legionaries. Bolter rounds exploded without effect against its ever-shifting hide and lascannon beams reflected harmlessly from its wings.

Lady Fiana stepped past Corswain, her whole body shaking as she pulled free her headband to reveal her third eye. The seneschal ripped away his gaze from her just before that warp eye was opened, and watched the beam of darkness that sprang towards the nephilla. It struck the creature full in the chest, detonating with a flare of dark energy, rocking it back a step but doing no more.

With a horrified gasp, Fiana unleashed her warp sight again, but this time the nephilla released one hand from its staff and stopped the beam with its palm. The energy coalesced around its fingers, playing from fingertip to fingertip like a miniature storm, while its snake head arched down to examine the flashing cloud of power. Eyes narrowing, it looked up at Fiana and thrust its hand back towards her, releasing the energy.

The Navigator shrieked as her body was engulfed by blackness, veins and arteries pulsing under her skin, blood streaming from eyes, ears and nose. She fell, and lay unmoving.

Corswain turned his attention back to the nephilla, and raised his pistol. Both of the creature's pairs of eyes were scanning around the chamber, necks craning to take in all of the Dark Angels. With a sweeping gesture, it sent a wave of power surging across the hall, smashing the legionaries from their feet. Corswain was hurled back with the others, crashing to his back beside the portalway.

Stretching up to its full height, the nephilla turned both heads towards the seneschal. It seemed to relax, staff held out to one side in one hand, the other stroking through the fires of its robes.