The space beyond was small and the light low. Stone-clad walls climbed to an arched roof. The names of every warrior who had ever called the ship home and died in battle marched over every surface, incised in gilded letters. The door sealed behind Sigismund. The low rasp-thump of machinery beating a dual pulse filled the quiet.

The remains of a figure lay under a shaft of dim light. They had tried to cut him from his armour, but armour and flesh could not be separated without ending what the Sons of Horus had begun. Tubes and pipes led from blocks of machinery and jars of dark fluid. The rattling bubble of breath drawn by a machine through fluid-filled lungs rose and fell in time with the pulse and thud of the tubes.

Sigismund stepped forwards. His armour growled. Something in the mass of sticky flesh and torn ceramite flickered and opened.

‘L… o…’ the sounds bubbled out. After a second, Sigismund realised it was a word, pulled out of the figure letter by letter as the machines gave it breath. ‘L… o… r… d…’

He knelt then, servos grinding, his gaze fixed on Boreas’ eye.

‘No,’ he said. ‘I am no lord here, my brother.’

‘Y…o…u…’ began Boreas. ‘You… li…ve…’

Sigismund nodded.

‘The tech-priests–’

‘I… know… I will… not… go to… the… iron sleep,’ said Boreas. Sigismund shook his head. There would be no rebirth as a Dreadnought for Boreas, no half-life of metal and war until he died a second time.

Sigismund bowed his head.

‘Why…’ The word brought his head up. Boreas’ eye was fixed on him, bright and unblinking. ‘Why… did… you want… to die?’

He saw the flash in his mind of the blades and faces of the Sons of Horus.

So many… Too many.

‘I…’ began Sigismund and now it was his words that faltered. He closed his mouth. The hiss-thump and gurgle filled the moment. ‘Atonement,’ he said at last.

‘For… what?’

‘For an oath broken,’ said Sigismund. The gaze of Boreas did not shift as he spoke, and the machines beat out the seconds. And Sigismund found himself speaking. He spoke of Euphrati Keeler, of the days after the first word of Horus’ treachery had found Dorn. He spoke of a vision she had given him of the future, and the choice that went with that vision: to be here now, as the darkness came to swallow the sun, and raise his sword against it, or to follow his primarch’s order and lead a fleet to strike at Horus in the earliest days of the war. He spoke of how he had chosen, and how he had returned with Dorn to Terra, and when the fleet that was his to command was lost, how he had told Dorn about his reason for returning and what he feared Keeler’s vision meant. And last he spoke of Dorn’s wrath at the reason.