Sigismund nodded, feeling the words he was about to speak gain weight on his tongue.

‘Turn the fleet,’ said Sigismund. ‘Cut them down.’

Kerberos detonated.

It was no small thing to destroy a moon. The agents of the Fabricator General had resisted. To them, such an act was a violation, the killing of machines – a tragic loss of function and knowledge. Rogal Dorn had not relented, and so it was done. Munitions had arrived on Pluto’s moons in vast numbers. Their magazines swelled with macro plasma cores, blocks of explosive and cylinders of accelerant. All of it had been done so that it would seem part of preparations for the coming war. The eyes of Horus amongst the defenders saw only stores arriving for a siege, and did not ask or think any more of it.

The tech-priests had done their work, layering in time-delayed overload routines into primary, secondary and tertiary reactor controls. Charges were set in the bloated munition stores, all synchronised to a single command that would make them all parts of a single, great act of destruction. The data-jinn that the tech-priests created to enact the design had needed to gestate for months in the data-looms of deep-void facilities, and when it was complete all those involved had the memories of what they had done removed. It was a thing of artistry and genius, a hymn to the limits of knowledge and machine-craft, but none of those who wrought it would ever wish to claim their due for their work. They gave it a name, though, a designation that wove its purpose with a whisper of forgotten dread.

They had named it Vanth-Primus-Nul.

As the Imperial Fists retreated, the data-jinn had begun its work. Incubated in the core data-reservoirs of each fortress-moon, it uncoiled into full being. Tentacles of code in a dozen machine languages reached through data-cables and photon lines and noospheric connections. From system to system it spread. It overwrote command codes and retasked servitors. Data altered, and cycles of unmaking began in the spirit of each machine it passed through. Even on the moons already in the attackers’ hands, Vanth-Primus-Nul carried on doing its work, increment by increment, silent and unseen. By the time the Iron Warriors and Sons of Horus had begun their assault on Kerberos in earnest, the process was already past the point where it could be undone.