'Yes, I believe you,' he said at last. 'What would you have us do?'

'Uriel!' cried Pasanius.

'I do not believe we have a choice, my friend,' said Uriel slowly.

'Think of what you are saying,' said Pasanius in disbelief. 'Whatever this bastard thing wants us to do can only be for evil. Who knows what we might unleash if we agree to do what it wants?'

'I know that, Pasanius, but what else can we do? Would you see Ultramar destroyed? The Fortress of Hera brought to ruin?'

'No, of course not, but—'

'No, Pasanius,' said Uriel evenly. 'Trust me. You have to trust me. Do you trust me?'

'You know I do,' protested Pasanius. 'I trust you with my life, but this is madness!'

'Then trust me now,' pressed Uriel.

Pasanius opened his mouth to speak once more, but saw the look in Uriel's eyes and simply nodded curtly.

'Very well,' he said sadly.

'Good,' hissed the Omphalos Daemonium, revelling in their defeat. 'There is a fortress many leagues from here, high in the southern mountains, and its master has something deep in his most secret vault that belongs to me. You will retrieve it for me.'

'What is it?' asked Uriel.

'It is the Heart of Blood, and that it is precious to me is all you need know.'

'What does it look like? How will we recognise it?'

The Omphalos Daemonium chuckled. 'You will know it when you see it.'

'Why do you need us for this?' demanded Pasanius. 'If it's so damned important, why the hell don't you just get it yourself?'

The Omphalos Daemonium was silent for a beat, then said, 'I have seen you with it and it is your destiny to do this. That is enough.'

Uriel nodded, hearing a distant, shrill cry on the air.

The Omphalos Daemonium heard the noise too and cocked its head, turning and marching back to the rectangle of red light that led back into the daemon engine and the hissing Sarcomata.

As it reached the shimmering doorway, it said, 'The delirium spectres come. They hear the beat of your hearts and their hunger tears at them. It would be wise not to be found by them.'

'Wait!' said Uriel, but the Omphalos Daemonium stepped through the doorway and he watched helplessly as it faded and vanished from the mountainside, taking their daemonic captor from sight.

A leaden weight of despair settled on Uriel's soul as the Omphalos Daemonium disappeared, and he dropped to his knees as he heard the cries of what sounded like a skirling chorus of air raid sirens.

He looked into the dead sky and saw a flock of hybrid, winged… things, flapping rhythmically on fleshy pinions towards them from the high peaks of the mountains.

'What the hell…?' said Pasanius, squinting into the sky.

'The delirium spectres,' said Uriel, scrambling over the ashen ground to retrieve his weapons.

'What do we do?' said Pasanius, belting on his pistol and slinging his flamer over his shoulder.

'We run,' said Uriel, as the madly screeching flock drew closer.

Black shapes against the white sky screeched as they descended from the heights of the mountains and streaked towards the two Space Marines. The delirium spectres filled the air with the wails of murder victims and Uriel could hear their agony in every shriek torn from their bodies.

He scanned the plateau for obvious hiding places, hating the idea of flight, but knowing that the Omphalos Daemonium had not lied when it had told them that it would be wise not to be found by these creatures.

'Uriel,' said Pasanius, pointing further up the steep slopes of the mountain to a narrow defile in the rock-face. 'There! I don't think they will be able to get in there.'

'Can we make it?'

'Only one way to find out,' said Pasanius, setting off for the scree slope.

Uriel buckled on his sword and ran after Pasanius, his breath ragged and strained in the toxic atmosphere. His back felt as if it was on fire, but he pushed aside the pain as he reached the slope and began climbing after Pasanius. The slope was rough, composed of dusty iron filings, craggy lumps of coal and twisted scoria. Pasanius's prodigious strength enabled him to scale the slope, albeit with great difficulty, but the loose incline gave Uriel no purchase and the harder he struggled, the further he slid back.

Screeching wails of obscene hunger echoed from behind and he risked a glance over his shoulder as the first of the delirium spectres dived from above.

'Uriel!' shouted Pasanius from a ledge above. 'Go left!'

He rolled to the left as the creature dropped from the sky, welded iron claws on its wings gouging the ground where his head had been.

He kicked out and the creature skidded down the slope, its fleshy wings beating the air in fury as it righted itself. Its shape was like that of some great, ocean-dwelling manta ray, an external skeleton formed of iron struts with its flesh a billowing sheet of patchwork human skin stitched to the metal. Screaming faces bulged across its leathery hide, a vicious ''o'' of a mouth edged in hundreds of needle-like teeth.

Another three creatures swooped from above, their jaws stretching across the entire surface of their skin and billowing wings flaring out to arrest their dives as they smashed into Uriel. The creature Uriel had knocked aside leapt into the air with a discordant howl as he struggled with the beasts that enfolded him, their teeth gnashing against his armour.

Pasanius shot the airborn delirium spectre, but his bolt passed clean through its flesh before detonating and it altered its course to swoop further up the slope to attack him with a deafening screech.

Uriel gripped the greasy flesh of the monsters attacking him and wrenched it from his armour, seeing anguished faces bulge from the surface of the skin and reach out to him. He punched through a thrashing jaw, his fist ripping through the taut skin as a flare of heat washed over him from above and he heard Pasanius shout, 'Get back!'

The beast thrashed in his grip as the others snapped and bit at him. He forced his other hand through the wound he had punched, rolling down the slope and dislodging the others. He gripped the flapping skin to either side and tore it from the iron frame, feeling the souls trapped within scream of their release.

Flickering lights and joyous cries erupted from the dying beast, and as the last soul departed, Uriel was left with an inanimate pile of torn flesh and metal in his hands. He hurled its remains aside as yet more of the creatures circled lower. Uriel drew his sword, slashing the energised blade through the flesh of the nearest delirium spectre, drawing a hysterical shriek of freedom from its jaws before it collapsed.

The last beast leapt towards him and he dived forwards, rolling and slashing high with his blade and hacking it into two halves as it passed overhead.

He heard another cry of release and saw a lifeless pile of iron struts and burning skin lying further upslope. Pasanius had his flamer out, spraying burning gouts of promethium into the air to discourage the other creatures from approaching too closely.

'Come on!' shouted Pasanius. 'I don't know how much longer this will hold them!'

Uriel sheathed his sword and stopped to grab two shorn lengths of iron from the corpse of the nearest monster before heading once more for the treacherous slope.

Driving the lengths of iron bar deep into the powdery shale like crude pitons, Uriel was able to climb the slope without too much difficulty while Pasanius kept the delirium spectres at bay with his flamer.

At last he reached the ledge and rolled onto his back as the delirium spectres closed in again. He drew his sword once more and slashed the first apart, feeling a grim satisfaction as it screamed in gratitude before its dissolution. Others burned in the fire, child-like laughter rippling from their blazing flesh as they died.