'All right. Where do we go from here?'

Askelon looked about the chamber. It was identical to the conduit room at the manufactory, only substantially larger. He nodded to the metal door across the chamber. 'That leads out into a sub-level beneath the main assembly floor. From there we'll be able to access almost every pan of the building.'

Nemiel checked his chrono again. It was little more than an hour until dawn. 'A building like this is bound to have catwalks along the upper storeys, correct?'

Askelon nodded. 'Three levels of them, in this case. You can look out over the entire assembly area from some of them.'

'Then that's where we need to be,' he said. 'Let's go.'

Kohl took point after that, leading the squad through the confines of the sub-level according to whispered directions from Brother Askelon, until they reached a narrow stairwell that climbed upwards into the assembly building proper. Weapons ready, they made their way carefully up the permacrete stairs, listening for the slightest sound of movement. Nemiel could hear the sharp crackle of arc torches and the snarl of power tools reverberating through the walls, the steel-on-steel noise like the sounds of a distant battlefield.

They climbed up several storeys, past one dimly-lit landing after another, until Nemiel signalled for a halt. 'This is far enough,' he said. 'We don't need to get all the way to the top; I just want a good view of what's going on,' he told them. He turned to Askelon. 'Is there any risk of sensors at this point?'

'No,' the Techmarine replied. 'We're past their detection perimeter at this point.'

'All right. Marthes, you and Vardus stay here and cover the stairwell. Kohl, Askelon and Ephrial, you're with me.'

Nemiel crouched at the plasteel door and cracked it slowly open. Beyond, the gantry-way was lit with red light from below. His autosenses picked up the reek of melted plas, petrochemicals and heated metal. Distantly, he could make out the sharp blurts and squeals of binaric cant, as well as a number of voices speaking in Gothic. The Redemptor concentrated, but he could make out what they were saying over the squalling of the machinery.

He surveyed the gantry-way carefully for as far as he could see, checking for any signs of movement, then went back and checked again. Satisfied there was no one within the immediate area, he opened the door the rest of the way and crept quietly onto the plasteel catwalk.

The assembly building was rectangular in shape, with an open floor plan surrounded by six huge niches that stretched from floor to ceiling. Giant servo arms were set into either side of these niches, able to climb to different heights along trackways set into the permacrete, and huge cranes hung from similar tracks high overhead. The Titans were assembled inside each niche, starting with the skeletal structure of the feet and working upwards to the head.

Nemiel found himself crouched on a section of third-storey gantry-way at one end of the building. The storeys above him were plunged into darkness, without so much as an emergency lamp burning. Below, red light rose up from the assembly floor like the glow of an actual forge. Gusts of hot air, stirred by industrial grade arc torches blew against his faceplate. A rustle of iron links, musical and cold, chimed from the deep shadows high above the floor.

Hundreds of chains had been suspended from the assembly building's ceiling, twisting and clinking together in the restless air. Each chain, more than fifty metres in length, had been strung with dozens of hooks, and on each hook hung a fresh corpse. Nemiel saw the bodies of Tanagran Dragoons, skitarii - even the mangled bodies of dead Praetorians - along with the smaller figures of tech-adepts and half-mechanical magi. Their corpses had been riddled by bullets or torn apart by energy bolts, sliced open by power claws or crushed by mechanical fists, and their fluids leaked from them in a steady, dripping rain onto the hulls of the enormous vehicles below.

There were six of them, Nemiel saw. Their chassis were so wide that they could only be arrayed in a single file that stretched from one end of the assembly building to the other. Their armoured hulls were supported by dual sets of treads on each of the vehicle's flanks, with a sloped front that rose like a sheer-sided hillock more than two storeys high. Void shield generators studded the vehicle's sides, along with automated quad-laser and mega-bolter emplacements, but Nemiel scarcely noticed them. His gaze was drawn to the enormous cannon built into the centreline of the vehicle's hull. A complicated series of hoists and giant braces surrounding the cannon's barrel indicated that it was meant to be elevated and fired like a conventional artillery piece. The aft section of each vehicle was segmented like the body of a giant insect, and appeared to be even more heavily armoured than the rest of the hull.

'What in the Emperor's name are those things?' Kohl hissed. It was the first time Nemiel had ever heard the sergeant taken aback.

Techmarine Askelon carefully eased into a crouch beside them. His eyes widened as he saw the machines on the assembly floor. 'Siege guns,' he said, his voice tinged with awe, 'but far larger than any I've ever seen before. Those look like macro cannons, fitted to a custom hull.' He pointed to the nearest vehicle. 'See those dual treads? Those aren't part of a contiguous drive train. They are distinct drive units, similar in size and power the ones used on Baneblade super-heavy tanks. There are three to a side, and that's just to form the foundation for each vehicle.'

Tech-adepts were crawling like ants over each of the war machines, working feverishly along the armoured hull beneath the rain of gore. Symbols had been scrawled in blood at regular intervals along each machine's flank, but Nemiel couldn't make them out at such a distance. The Redemptor noticed that he vehicle closest to them had a large, open hatch on the top deck, to the right of the huge gun. 'What do you make of that?' he said, pointing to the two tech-adepts working in the well beneath the hatchway.

Askelon leaned slightly forward, peering intently at the opening. His eyes widened. 'It's an MIU interface chamber,' he said, 'A neural interface link, much like we employ on our Titans. It looks like they're refurbishing the control leads and making it ready for use.'

'So a single operator could control one of these behemoths?' Nemiel said.

The Techmarine nodded. 'Of course. They're big, but far less demanding than a bipedal Titan,' he replied. 'And the MIU makes it nearly impossible for them to be used if captured.'

Nemiel nodded grimly, his gaze rising to the collection of corpses dangling in the air before them. 'Now we know what happened to the Dragoons covering the southern approach,' he said, his voice thick with revulsion. 'Not to mention a good many of the forge's own personnel. Magos Archoi is a madman. This whole thing smacks of some obscene, superstitious ritual. How could someone like Horus Lupercal be connected to such debased behaviour?' Memories of the foul things he'd witnessed at Sarosh rose unbidden in Nemiel's mind. He forced them aside with an effort of will and a savage shake of his head.

Kohl tore his gaze away from the repellent sight and caught a glimpse of movement on the assembly floor. 'Here comes the high priest himself,' he growled, pointing to the narrow lane at the right of the parked war machines.

Nemiel straightened, craning his head around to see Magos Archoi walking down the line of vehicles. A pair of tech-adepts followed a discreet distance behind the magos, their hands tucked into their sleeves, while a knot of four uniformed men dogged Archoi's heels and studied the siege guns critically. One of the men was conferring with the magos, speaking to him in urgent tones. It took a moment for Nemiel to recognise the uniform he wore.