Astarte acknowledged the Emperor is smarter than any of them.

"And the Sigillite had been right. Things had slipped too far, and global conquest required soldiers altered at the genetic level. By the time she was brought into His confidence, the Legio Custodes was already in active service, but the secrets of their painstaking creation were kept tightly under wraps, and in any case they had never been destined for mass production. He had wanted her for something different – armies of a far greater size, built for rapid deployment, bulk-produced according to standard biological templates.

The first subjects were disasters, shambling creatures little better than the flesh-puppets they were intended to take on. The processes were subsequently honed under the privations of constant warfare, in clinics and laboratoria that were kept mobile lest they be discovered and destroyed. Some of the lore deployed was old and imperfectly understood; some of it was new and volatile. Throughout it all, He kept them all working punishingly hard, inspiring with a word or a gesture, refining their crude initial attempts when necessary, opening up new vistas of possibility, persuading, teaching.

She had often wondered, even then, how far their own work was really His, conducted indirectly through mental suggestion or inspiration. He knew so much more than any of them, and yet He could not be everywhere at once, and so they were necessary, His tools, His band of willing acolytes.

She flattered herself that some of the key insights had been hers. Having devoted so much of His intellect and energy towards perfection, she came to believe He struggled with the messier business of compromise, and thus lesser minds had their uses. There was never time for perfection, and so the Cataegis were always a compromise. They were the best that could have been created under such conditions, but nobody believed they were permanent.

That had always made her anguished, just as it had before. Under their ferocious advance, an entire world was slowly brought to heel, but there was still the old price to pay, of pain and physical corruption, only this time set against the loftier goal of recovered civilisation. So even as the Thunder Warriors reached their apogee of power and fame, their replacements were being planned. These were to be more stable, more enduring, more flexible and more disciplined. They would be created in greater numbers, manufactured in batches just like the standardised weapons that were by then pouring off Imperial production lines. Most importantly of all, they would be permanent.

‘Your progeny, Astarte,’ He had remarked once, in a rare moment of possible levity. ‘Your legacy.’

That wasn’t true. Not strictly. Everything emanated from Him ultimately, including this programme, but there had been times, times of weakness, when she had been driven into fatigue by the endless work, when she had given into that dangerous conceit, and thought of them, for a moment, as hers.

But then the day of destruction had come, when the vaults had been breached and the instigator subjects destroyed. They had been central, those twenty primal components, designed to keep the new Legions from suffering the instability of the old. Rather than a patchwork of many gene-templates, they had been there to provide a solid anchor, a means by which excess could be tethered, and now they were gone."