It was a thought he could scarcely bear.

‘Magos?’

He looked up. Nayl was beckoning to him.

There was a hatch at the end of the hallway. It was clearly Imperial tech, a heavy duty hatch like a shift-ship’s air-gate. It looked incongruous, as if it had been retrofitted into the old, eerie architecture of the building.

Why would you put something that massive and secure into a place where polished wooden doors with silver handles were otherwise sufficient?

And if the answer to that question was security, what did you keep on the other side?

And why would you then leave the hatch wide open?

Drusher joined Nayl, and they peered in through the hatch.

The chamber beyond was vast and cylindrical. Drusher guessed it was the interior of one of the fortress’ main towers. All the original floors and stairways had been removed. The curved walls soared up into darkness above them and dropped away into darkness far below.

The walls had been etched with lines. It was script. Hundreds of thousands of lines of writing, covering every centimetre of the interior walls, in perfect, uniform rows. It must have taken decades for skilled artisans to inscribe it all. Drusher wondered what it said. He was too far away to be able to read any of it.

The hatch led out onto a railed, metal landing inside the hall. The landing hung like a balcony under the hatch. Open metal steps led down to other platform stages below and several further above them. The platforms and connecting steps were all standard template units, Imperial build, the kind seen in manufactories and promethium plants and all manner of workspaces in human habitations across the Imperium. There was something oddly reassuring about their familiarity, but, like the hatch, they seemed uncomfortably out of place in the setting.

Around them, filling the main space of the tower, was vast technology of another sort. This was the source of the constant humming. To Drusher, it looked as if someone had taken all the complex inner mechanisms of an antique mechanical timepiece, enlarged them, then slotted them carefully into the drum of the tower. Cogs, gears, springs and winders whirred and moved in perfect, oiled precision. The crude STC platform sections and steps had been suspended inside the vast brass mechanism, allowing access to it at different levels. On some platforms, powerful cogitator units and workstations had been bolted in place, connected by sheaves of cables and data wires to the Great Machine. Drusher saw their screens and displays flickering with bright lines of changing data: monitor positions from which to study and perhaps even operate the strange and ancient mechanism. The air was dry and smelled of metal filings, oil and warm power systems.

There was a large platform directly below them, a circular gantry fixed in the centre of the tower’s interior. In the middle of it was a square iron cage, crudely heavy and filthy black.