The red glow and hateful cacophony of noise swelled until they passed into the colossal cavern beyond.

'Oh, no…' breathed Uriel as he finally laid eyes upon the Halls of the Savage Morticians.

'What the hell… ?' said Vaanes, his face lit by the diabolical, blood-red glow of the cavern.

Its far side was lost to sight, the ribbed iron walls soaring to distant heights where throbbing machines and mighty turbines roared and seethed. Great cables and looping tubes ran across the walls and curving ceiling, dripping a fine mist of bodily fluids to the stinking rocky floor. Tiered levels of darkened cages, similar to the ones Uriel had seen in the mountain flesh camp, circled the walls of the cavern, troughs running below each one and pipes running from heavy bladders suspended from the roof.

As he was forced into the cavern, Uriel felt a sudden dullness assault his senses, feeling as though under the effects of a massively powerful pain balm. Everything seemed bleached of its colour and taste and smell, as though every sensory apparatus of his body was being smothered.

The floor of the cavern was rough and irregular, random structures and gibbets built upon one another with mortuary tables - some occupied, some not - scattered in a haphazard fashion around the chamber. Drawn by the noise of the elevator cage, black-robed monsters threaded their way through the cavern, scuttling forwards on an assortment of wildly differing forms of locomotion. Some came on spidery limbs, others on long assemblies of stilts, while others rumbled forwards on spiked track units. Their waving arms were an eclectic mix of blades, claws, clamps, bone saws and whirring cranial drills. No two were alike, but each one bore the scars of massive, self-inflicted surgeries, their forms repugnant and evil.

Each displayed a corrupted version of the skull and cog symbol of the Adeptus Mechanicus upon its robes, though Uriel found it hard to reconcile these abominations with the priests of the Machine God. Their skins were dead and they babbled in a series of unintelligible clicks that sounded like gibberish to Uriel.

Onyx stepped into the cavern, closely followed by Sabatier. The Savage Morticians quickly surrounded them, prodding Onyx with pincer arms and stabbing at him with needles.

'A gift from Lord Honsou,' said the daemon symbiote, ignoring the examination. Finding nothing of worth on his daemonic frame, the fell surgeons moved on, approaching the warrior band with a sick, skeletal lust in their soulless eyes. One of the nightmare monsters turned back to Onyx and Uriel recognised it as the one they had seen upon entering the tower. Its mouth opened and a hissing, clicking language emerged.

'Your gift acceptable,' translated Sabatier. 'You get to leave unsurgeried.'

Onyx nodded, as Uriel took in more of the dark wonders displayed throughout the cavern. But immediate and terrifying as the forms of the Savage Morticians were, it was to the centre of the chamber that Uriel's gaze was irresistibly drawn.

Held suspended over a bubbling lake of blood by a trio of thick chains and gleaming silver awls piercing its chest and torso was a bloated red daemon, ancient and swollen with crackling energies. The flesh of its body was scaled and thick tufts of shaggy, matted hair ran from its horned skull down the length of its back. Its cloven hooves clawed the air and as it thrashed impotently against its fetters, Uriel could see great wounds on its back where a pair of wings had been surgically removed. Its chest heaved violently in time with the booming echo that filled the chamber and Uriel knew that this imprisoned daemon must be the source of the noise.

'"You will know it when you see it…"' said Pasanius.

'What?'

'That's what the Omphalos Daemonium told us, isn't it?'

'About what?' asked Uriel.

'The Heart of Blood,' said Pasanius. '"You will know it when you see it."'

Uriel looked up at the bound daemon, realising that Pasanius was right. This could be none other than theHeart of Blood, the daemon thing that according to the tale Seraphys had told, had outwitted the Omphalos Daemonium and bound it to an eternity of torment within the firebox of a terrifying daemon engine.

Surrounding the lake of blood were hundreds of upright coffins of black iron with gurgling red tubes piercing their tops. In each coffin lay a chanting, gold-robed sorcerer, their withering bodies pierced by scores of exsanguination needles that fed the hissing lake beneath the imprisoned daemon with their blood. A pulsing tube rose from the lake, penetrating the daemon's chest as the psykers' blood was forced into its immaterial flesh. The daemon writhed in agony above the lake, a rippling haze of psychically dead air rising from the warp entity's skull and filling the pinnacle of the chamber. The daemon's torment at its confinement was plain and now that he focussed on it, Uriel could clearly see that this was the source of his deadened senses.

'Lord Honsou requests that this one,' said Onyx, indicating Uriel, 'be fed to the daemonculaba, while the one with the silver arm has it removed and brought to his inner sanctum. Is this acceptable?'

The creature lurched forwards, lifting Pasanius with a hissing claw that sprouted from its pneumatic leg assembly. A whining blade snapped from the armature on its wrist and with brutally efficient cuts, sawed the armour from Pasanius's upper arm, exposing the muscled flesh of his bicep and the junction of flesh and metal.

'Put me down, Chaos filth!' yelled Pasanius, kicking out at the withered chest of the Savage Mortician. It hissed, as though unused to such defiance and a thick needle extended from beneath the saw-blade and stabbed through Pasanius's breastplate. Within seconds the sergeant's struggles had ceased and the monster handed him on to another of its surgical brethren.

Uriel surged forward as Pasanius was borne away, but his lethargic senses slowed him and Onyx stopped him with a bronze blade at his neck.

'Don't,' he said simply. 'His fate will be nothing next to yours.'

Uriel said nothing as the Savage Morticians surrounded them and gathered them up in their mechanical claws.

'I will kill you,' promised Uriel as he was lifted, struggling, from the ground. 'You had best shoot me now, for I will see you dead if you do not.'

'If the powers decree that is my fate, then so be it, but I think you are wrong. You will die in this place, Uriel Ventris,' shrugged Onyx before turning on his heel and re-entering the tunnel that led to the elevator cage with a grateful-looking Obax Zakayo.

Uriel fought uselessly against the claws of the Savage Mortician, but its strength was enormous and he could not move. Its dead face hissed as it examined his body in detail. Gleaming arms of bronze held him immobile while pincers and needles pierced his flesh.

A clicking arrangement of spindly rods extended from the monster's hood, telescoping outwards and bearing a meshed mouthpiece that snicked into place before its toothy jaws. Sharp drill-bits clicked from the mouthpiece and burrowed into the Savage Mortician's metal jaw, sending dusty flurries of metallic flesh flying.

The mesh unit hissed with static and the Savage Mortician said, 'You are to be fed to daemonculaba. Waste of flesh. Much surgeries could be done with you. Things unknown become known. Others will do.'

'What are you going to do with us?' shouted Vaanes, struggling helplessly in the grip of a tall, black-robed monster that travelled on hissing mechanical legs, reverse jointed like those of a Sentinel.

'We are the surgeons of demise,' said the monster. 'Monarchs to the kingdom of the dead. Will show you the meaning of pain. Abacinate you then open you up with knives. Take what we want. Make your flesh our own.'

The dark priests of flesh and machine stalked off through the red-lit cavern, carrying the members of the warrior band towards the experimentation tables, animatedly discussing their proposed surgeries with one another in their clicking, machine language.