He pushed himself upright, seeing Pasanius next to him, retching onto the metallic ground. His friend's face was drawn and hollow, as though the weight of the world had settled upon his shoulders.

'Get up,' said a grating voice behind him and a flood of memory filled Uriel's skull. Daemon. Daemon engine. He fought to stand, but his flesh was still adjusting to its return to existence and he could only stumble to his knees.

Before them stood the Omphalos Daemonium, gigantic and monstrous in its blackened and ancient suit of power armour. Behind their captor was a shimmering, impossible rectangle of seething red light, a doorway back to the hellish interior of the daemon engine.

It carried its billhook and stood ankle deep in the powdery shale of the ground. Their weapons, Uriel's sword and bolter together with Pasanius's pistol and flamer rested against the rocks beside it. White reflections of the dead sky glittered on its shoulder guards and it seemed to Uriel that the grinning, visored skull there burned with even more malice than before.

'You will need to restore your equilibrium soon, Ultramarines,' said the daemon thing with an echoing chuckle. 'The delirium spectres will hear the pounding beats of your hearts and such morsels as you shall not go unnoticed for long.'

'The what?' managed Uriel at last.

'Monsters,' said the giant.

'Monsters?' repeated Uriel, gritting his teeth and finally climbing to his feet. Pasanius picked himself up and stood beside him, his face ashen, but angry.

'The skins of murderers stitched across desecrated frames by the Savage Morticians and filled with the mad souls of those who have died by their hands,' explained the Omphalos Daemonium. 'They hunt in these mountains and you will know them by the cries of the damned at your heels.'

'Where are we?' said Pasanius. 'Where have you brought us?'

'This is Medrengard, world of bitter iron,' said the Omphalos Daemonium, pointing at something behind the two Space Marines. 'Domain of the daemon primarch, Perturabo. Can you not feel his presence on the air? The malice of a being who once walked with gods and is now cast down to dwell beyond the realm he once bestrode. Look upon this ashen world and despair!'

Uriel turned to where the Omphalos Daemonium was pointing, the breath catching in his throat as he saw the desolate vista before him.

They stood on a high, rocky plateau above a sweeping, grey hinterland of utter wretchedness. Far below them on the dismal steppe was a world of death. Uriel had thought the sweltering cavern of the daemon engine had been a vision of hell, but it had been no more than a prelude to this soul-destroying desolation. Vast expanses of industrial heartland sprawled across the surface of the world: steel skeletons of factories, mountains of coal and reddish slag and mighty, belching smoke stacks. Flames burned from blasted refineries, the pounding of mighty hammers and the clangourous screech of iron on stone audible from hundreds of kilometres away.

Uriel had seen pollution-choked hive worlds, planets teeming with uncounted billions who toiled ceaselessly in filthy, smog and soot-choked death worlds, but they were garden paradises compared to Medrengard.

He had even set foot on the iron surfaces of Adeptus Mechanicus forge worlds, the hallowed domains of the priests of the Machine God. He had been awed by the scale of their pounding infrastructure, their every surface given over to colossal manufactorum and cathedral forges, but even the mightiest of these worlds was but a village smithy compared to Medrengard.

Rivers of molten metal snaked like channels of lava and evil clouds of smoke wreathed each tall tower and fanged chimney in a halo of lethal fumes.

A vast, dark range of mountains towered over it all: blasted black rock where no living thing had ever lived or ever would. The peaks seemed to scrape the sky itself: the jagged stumps of the mountains a dozen or more times taller than the highest summit of Macragge. Uriel felt his blood chill as his eyes travelled up the terrifying heights of the enormous crags, seeing vile tendrils of noxious black smoke writhing from behind the mountains and clawing impossibly into the sky.

Strange turrets reared beyond the peaks and Uriel knew with awful certainly that some nightmare city lay concealed and brooding in the deep, dark valleys of that damnable mountain range. A city where walls and bastions spread across the ground and distant domes fouled the rock like fungi after the rain. It was a hideous, dead-ringed outpost of malice that was rightly abhorred by all living things. Tarnished steeples and stained walls, deathly weed-tangled spires and empty halls were filled with limping and shuffling ghosts in rags who blindly obeyed the loathsome will of the city's diabolical master: the daemon primarch Perturabo, lord and master of the Iron Warriors.

'The hate…' whispered Uriel. 'So much hate and bitterness.'

'Yes,' said the Omphalos Daemonium. 'Imagine all the rank bitterness I smell within you - poisoned and grown strong by millennia of vengeful brooding, and it is still but the merest fraction of how much a living god can hate.'

Uriel closed his eyes to shut out this nightmare vision, understanding that to take even a single step towards the dreadful city was to die, but its cyclopean immensity was etched forever in his mind such that nothing could ever remove it.

The futility of existence in the face of this nameless horror was almost too great to bear and he raised his eyes to the dead sky, its soul-destroying emptiness preferable to Perturabo's baleful city. The ghostly black tendrils squirmed through the sky and he saw that they poured towards the solitary thing to stain its emptiness.

A vast black sun, its surface so dark that its darkness was not simply the absence of colour and light, but such that its fuliginous depths sucked all life and soul from the world.

Pasanius wept at its horrible, crushing weight and Uriel was not surprised to find that he too shed tears at the sight of such an abomination against nature.

'Emperor protect us,' he whispered. 'This is…'

'Aye,' said the Omphalos Daemonium. 'This is the place you call the Eye of Terror.'

'Why…?' gasped Uriel, tearing his gaze from the morbid sun. 'Why here?'

'This is the end of your journey. The place where you will fulfil your oath.'

'I do not understand.'

'That matters not. The things you seek to destroy, the daemonculaba, are on this world, shuttered away in the darkness, far from the sight of man in a great fastness fashioned from madness and despair.'

'Why would you bring us here?' demanded Uriel, a measure of his self-control returning. 'Why would a creature of Chaos seek to aid us?'

The Omphalos Daemonium laughed its booming, discordant laugh and said, 'Because you are to do my bidding, Uriel Ventris.'

'Never!' snapped Uriel. 'We would die before aiding a beast such as you.'

'Perhaps,' agreed the giant warrior. 'But are you willing to sacrifice all that you have fought to protect by defying me? Everything you have sacrificed and everyone you have bled to save will be washed away in an ocean of blood if you do.'

'You lie,' growled Pasanius.

'Foolish morsels. What need have I of lies? The Architect of Fate has lies enough for this universe: the Lord of Skulls demands no such pretences. I know what you saw as we travelled the bloodtracks, your world afire and your people dead, ashes on the wind as it burned to death.'

The Omphalos Daemonium took a ponderous step towards them, its billhook lowered to aim at Uriel's chest.

'I can make that happen,' it promised. 'All the splintered futures you saw can be shaped and I can ensure that your precious home dies screaming in the flames. Do you believe that?'

Uriel stared into the leprous yellow eyes of the daemon and knew with utter certainty that it could do the things it spoke of - Macragge destroyed, Ultramar gone…