'Where are they taking them?' said Leonid.

'For burial perhaps,' suggested Uriel.

'I didn't think the Iron Warriors cared too much about honouring the dead.'

'Nor did I, but why else bring the fallen back inside the walls?'

'Who knows, but I have a feeling we'll be finding out soon,' said Vaanes, gloomily.

'If it is connected to our mission, then yes, you're right,' said Uriel continuing down the stairs to the interior of the fortress. The stone steps reflected the light from the purple clouds above the iron tower and Uriel wondered what dark practices and plans had been hatched within its cold depths. The stairs curled down the diffside of the mountain, widening until they formed a long processional that opened into a bone-flagged esplanade with iron execution poles spaced at regular intervals.

Corpses hung from three of the poles, dry and desiccated, their skin sagging and blotchy. Uriel ignored them, staring into the dark mass of hammering buildings and winding, haunted streets that led towards the tower.

The same emerald glow that suffused the mountain's interior from above was stronger now that they had reached the bottom of the stairs though, the source of its sickly glow was invisible. The manufactories towered above them, the noise of grinding pistons, hissing valves and clanging hammers echoing from all around them and Uriel tasted ash and hot metal on the air.

'Let's go,' said Uriel, as much to galvanise himself into action as to issue an order.

He set off with his bolter at the ready, the Space Marines of the warrior band following close behind him, instinctively falling into a defensive formation with Leonid and Ellard at their centre and all their guns pointing outwards.

A chill of the soul pierced every warrior as they entered the evil shadows of Khalan-Ghol, the chill of plunging into the black waters of an underground lake that has never known the warming touch of a sun. Uriel shivered, feeling a thousand eyes upon him, but seeing nothing and no one moving around them.

'Where are all the people we saw from above?' asked Vaanes.

'I was wondering the same thing,' said Pasanius. 'This place looked well occupied.'

'Perhaps they are hiding from us,' replied Ellard.

'Or perhaps it just seemed occupied,' suggested Uriel, casting wary glances all around him, catching fleeting snatches of movement from in the shadows. 'This place will confound our senses and try to mislead us with illusions and falsehoods. Remember what happened in the tunnel.'

The streets and narrow alleys of Khalan-Ghol twisted at random, zigzagging and twisting around until Uriel could not say for sure which way they were even heading any more. He wished he still had his helmet, but wasn't sure that even its direction finding auspex would be any use here. He couldn't see the iron tower in the cramped streets and had to trust that his instincts were leading them towards it.

Tall shadows danced on the walls, capering along the sides of the black brick buildings, as though racing them through the interior of the fortress. The darkness pressed in around them, and Uriel found himself absurdly grateful for fleeting snatches of the white sky above them. He could feel the power of the black sun above him, but kept his eyes averted for fear of the madness it promised in its fuliginous depths.

Tinny laughter, like a child's, seeped from the walls and shadows and Uriel could see the Space Marines were greatly unsettled by such a plaintive sound. He was reminded of the joyous cries the delirium spectres emitted on their death and wondered if there were similar creatures lurking somewhere nearby.

It seemed that for hours they wandered, lost and misdirected by the insanities of the daemon city. Uriel could find no landmarks upon which to base his choice of direction, the iron tower obscured by the looming sides of the windowless forges and the impenetrable shadows cast by the black sun.

Eventually, he called a halt to their march and ran a hand across his sweat-streaked scalp. There was no rhyme or reason to the layout of the fortress, if even such a thing truly existed. Travelling down the same street was no guarantee of arriving at the same place and doubling back did not return them to whence they had begun.

Impossible physics misdirected them at every turn and Uriel was at a loss as to how to proceed. He squatted on his haunches and placed his gun across his thighs, resting his head against the crumbling brickwork of the building behind him.

He could feel the pounding of heavy industry through the building's fabric, but of all the weirdly angled structures they had passed, they had seen neither window nor entrance to them, simply smoking chimneys and steaming vents.

'What now?' asked Vaanes. 'We're lost aren't we?'

Uriel nodded, too weary and soul sick to even reply.

Vaanes, slung his bolter across his shoulder, as though he had expected no other answer. He looked towards either end of the narrow, enclosing street, its surface black and oily, with the rainbow sheen of spilt promethium to it.

'Is it just me or is it getting darker here?' he asked.

'How can it be getting darker, Vaanes?' snapped Uriel. 'That damned black sun never sets, never even so much as moves in the sky. So I ask you, how can it be getting darker?'

'I don't know,' hissed Vaanes. 'But it is. Look!'

Uriel rolled his head around and saw that Vaanes was right. Creeping liquid shadows were slithering up the walls, swallowing the light and obscuring the surfaces of the buildings they climbed. Inky black, the shadows rippled from the walls, spreading like slicks across the ground and rearing up at the ends of the cobbled street to enclose them.

'What the hell is going on?' gasped Uriel as the sinister, impossible shadows began to coalesce before them, nightmare pools of foetid black iridescence that crept across the walls and street towards them from both front and back.

They drove stinking clouds of vapours straight from the abyss itself before them, vile toxic fumes and indescribable pollutants. Shapeless congeries of protoplasmic bubbles erupted across their amorphous forms, and Uriel now saw the source of the pallid, emerald glow that suffused the city as myriad temporary eyes formed and unformed in the hideous depths, glowing with their own luminescence.

'What are they?' he cried as the slithering mass of filthy, stinking creatures - or creature - oozed forwards.

'What does it matter?' shouted Vaanes. 'Kill them!'

Bolters fired explosive bolts into the heaving mass of corruption, exploding within the jelly-like mass of the things' bodies and the overpowering stench of chemical and biological pollutants gusted from the wounds.

Uriel caught a breath of the fumes and immediately dropped to his knees and vomited copiously across the ground. Even the formidable biological enhancements of a Space Marine were unable to overcome the sickening, horrific stench their bolters had unleashed.

More and more Space Marines dropped to the ground, retching and convulsing at the foulness of the creatures.

'Pasanius!' gasped Uriel. 'Use your flamer!'

He could not tell whether his battle-brother had heard his exclamation, but seconds later Pasanius bathed the advancing beasts in sheets of flame from his hissing weapon. The fires engulfed the beasts, leaping high and burning with terrifying force, as though they contained every flammable substance known to man.

Crackling ooze burned with a white flame and Pasanius switched his aim to the approaching shadow creatures behind them. More liquid flame sprayed and the deafening cries of the burning creatures reached new heights as they burned. Insensate eyes immolated and new ones formed in the fluid flesh of the beasts as the flames burned them. Eye-watering fumes were released from the conflagration, but even though it seemed the beasts were in pain, they did not retreat, holding them trapped within the narrow street.