Deep within its insane structure, it might have once resembled an ancient steam-driven locomotive, but unknown forces and warped energies had transformed it into something else entirely. The thunder of its arrival could be felt by senses beyond the pitiful five known to humankind, echoing through the planes that existed and intersected beyond the veil of reality.

Behind it came a tender of dark iron and a juddering procession of boxcars, their timbers stained with aeons of blood and ordure. Uriel knew without knowing that millions had been carried to their deaths in these hellish containers, carried to whatever loathsome destination this horrifying machine desired before finally being exterminated. The vast daemon engine slowed, the sleepers driven beyond sound in their torment as the towering machine halted at the edge of the platform.

Uriel thought he heard booming laughter and the grinding squeal of warped timber doors sliding open on runners rusted with gore.

Gusts of blood-laced steam hissed from the armoured hide of the Omphalos Daemonium and malevolent laughter rippled through them as they writhed on evil business of their own. Each tendril thickened and became more solid as they wormed towards the Space Marines and Uriel said, 'Stand ready.'

The tendrils of smoke vanished without warning and in their place stood eight figures, each wearing a featureless grey boiler-suit and knee-high boots with rusted buckles along the shins. Each carried a fearsome array of knives, hooks and saws on their leather belts.

Their faces were human in proportion only, flensed of the disguise of skin and glistening with revealed musculature. Crude stitches crisscrossed their skulls, and when they turned their heads as though hunting by scent, Uriel saw they were utterly featureless save for distended and fanged mouths. They had no eyes, nose or ears, only discoloured swellings that bulged and rippled beneath their fleshless skulls.

'Daemons!' shouted Uriel. 'Foul abominations! Come forth and die on my blade.'

A daemon's patchwork face swung towards him, tumourous tissue in its neck bulging with horrid appetite. None of the foul creatures moved, content merely to watch the two Space Marines as a billowing cloud of steam vented from the side of the vast daemon engine. With a clang of locks disengaging, a thick iron door squealed open and a gigantic figure stepped onto the platform.

Standing head and shoulders above them, the giant wore a clanking, mechanical suit of riveted iron plates and thick sheets of melted, vulcanised rubber. Over its rusted armour it wore a charred apron, and a crown of blackened horns sprouted from a conical helmet with a raised visor. For all its crude fabrication and disrepair, Uriel recognised the armour as impossibly ancient power armour, such as had been worn by warriors of legend many thousands of years ago. The stench of scorched meat enfolded it, together with a crackling sensation of depraved evil and unquenchable rage.

One shoulder guard was studded with star-shaped rivets, the other emblazoned with a symbol of ancient malice that both Ultramarines recalled from the depths of righteous anger instilled in them by Chaplain Clausel's daily Litanies of Hate. A grinning, iron-visored skull that once was the heraldry of a Legion that had fought for the Emperor in hallowed antiquity, but was now a symbol of unending bitterness and hatred. It was a symbol that now belonged to the most lethal foes of the Imperium: warriors of unutterable evil and malice - the Chaos Space Marines.

'Iron Warriors…' hissed Uriel.

'The Betrayers of Istvaan,' growled Pasanius.

The figure carried a long, iron-hafted billhook, the broad, curved blade rusted and pitted with reddish brown stains. A pair of burning yellow eyes, like sickly, dying suns, shone from beneath the helmet as the figure took a heavy step towards them, the skinless daemons moving to stand behind it.

'Deadmorsels feed the new fire, blood is supped by the faceless Sarcomata, and flesh of man will come with me,' said the figure, its voice like rusted metal on their skulls.

It gripped its enormous billhook in one blackened, burned hand and beckoned them impatiently towards the hissing daemon engine with the other.

'Come!' boomed the giant. 'I have purpose for you. Obey me or the Slaughterman turn you into dead-morsels! I am the Omphalos Daemonium and my will drives this suit of flesh, and it will turn you into dead-morsels! Now come!'

Uriel felt sickened even being near this thing of Chaos. Could it really believe that they would willingly have truck with such evil? The featureless daemons, which Uriel guessed were the Sarcomata the Omphalos Daemonium spoke of, spread out on the platform, unhooking long, serrated knives from their belts.

'Courage and honour!' yelled Uriel, leaping towards the nearest of the Sarcomata and stabbing for its belly. His sword passed straight through the creature, its form transforming into a cackling pillar of red steam. He pulled up in surprise, grunting in pain as the beast's form coalesced beside him and its blade slashed across his cheek. Another darted in, its rusty blade stabbing into his neck. He twisted free of the weapon before it could penetrate more than a centimetre and swung at his new attacker. Once again, his assailant flashed to steam before his blow could land and Uriel found himself off balance as another knife blade laid his cheek open to the bone.

'Burn, Chaos filth!' roared Pasanius and sprayed a blazing gout of promethium at the giant Iron Warrior. The volatile chemical flames licked hungrily at the giant, but no sooner had the fire taken than it guttered and died.

The creature's booming laughter echoed from the sides of the arena. 'I have been a prisoner in flames for aeons and liveflesh thinks it can burn me!'

Pasanius slung his flamer and reached for his pistol, but, with a speed that belied its ungainly form, the Chaos creature stepped forward, wrapping its blackened fingers around Pasanius's throat and hauling him from his feet.

Uriel slashed at the Sarcomata as they surrounded him, each thrust and sweep of his sword hitting nothing but chuckling tendrils of steam that vanished only to reappear elsewhere to cut him. Clotted blood caked his face and he knew that he could not fight such foes for much longer.

He saw the giant in the rusted armour lift Pasanius from his feet and hurl him through the iron door the Omphalos Daemonium had first stepped from, and surged towards the Chaos creature. He could not fight foes that could disappear at will, but he swore that this traitor from the elder days would die by his hand. He swung his sword towards the Iron Warrior, the blade wreathed in pellucid flames able to cut through armour and flesh with equal ease.

The sword struck his enemy full square on the chest, but the blade simply clanged from the heavy iron plates of his armour. Uriel was. amazed, but drew his arm back to attack again. Before he could strike, the Iron Warrior's fist slammed into his face, sending him sprawling across the platform.

He fought to regain his senses, but the Sarcomata surrounded him, their blackened fingers reaching hungrily for him. Their touch felt like rotted meat, wriggling with the suggestion of maggots and freshly hatched larvae. Their dead skin masks were centimetres from his face, their breath like a furnace of cadavers. They moved their undulating faces around his, as though tasting his scent, their fearsome strength pinning him to the ground.

'The Sarcomata favour you. Ultramarine…' laughed the giant, striding across the platform towards him. 'They are corruption of spirit given form and purpose. Perhaps they sense a certain kinship?'

Uriel waited for death as one of the Sarcomata lowered its mouth to his bared neck, but the Omphalos Daemonium had greater purpose for him than mere murder, and roared in impatience.