Mersadie was looking at the arrangement of symbols on the brass disc. She read the alignments, and memory unfolded the meanings in her mind from old parchments that she had thought mere curiosities when she’d read them. She read the position of the planets and the meanings of each of the symbols brought into concordance with them. She looked up at Keeler.

‘This is not just a metaphor, is it? These symbols are not based on the planets, they are the planets. This is a design. A ritual alignment.’ She stopped. The glass was shaking in the window frames. The warm dawn light had darkened.

‘Marked by blood and slaughter. As above, so below,’ said Keeler. ‘This is the dimension that Rogal Dorn does not see. If Horus can bring this into being, then the Praetorian’s defences will mean nothing. You must reach him. You must tell him before it is too late.

‘Remember!’ Suddenly she was shouting. ‘Remember what you have seen!’

And the circles of symbols rose before Mersadie, no longer stone and metal but burning in the air. She felt them press against her mind, unfolding into inference and meaning that she could not comprehend even as they poured into her.

‘Why me?’ called Mersadie over the howl that no longer sounded like wind. Light was draining from the dream. ‘Why have you asked me to do this?’

‘Because I cannot,’ said Keeler. ‘And because Rogal Dorn believed you before and will again. You showed him the truth of Horus turning on the Emperor. He will believe you.’

‘I am in a cell – how can I reach him?’

‘A way will open,’ said Keeler, her voice lifting over the howl of the rising wind. ‘But you will have to walk it.’ The floor of the room was shaking. The sky outside was bruised purple and iron. ‘They will try to stop you,’ said Keeler’s face in the dream. ‘Old friends and enemies alike. They will come for you.’

A vase toppled off a side table. White flowers and water scattered onto the floor.

‘How long until Horus comes?’ she shouted.

‘He is already here.’

The glass in the window shattered. The storm wind billowed in. Mersadie could smell ash and fire.

And her eyes opened to a world filled with the scream of sirens.

Void Fortress 693, Trans-Plutonian Gulf

‘Three minutes to impact.’

The voice blared in the dark. Saduran kept his eyes closed, his thoughts still, his heartbeats rising. The double rhythm was still an alien surge through his blood.

‘Blood on the stars,’ came the call from Ikrek, and the echo roared back from the mouths of the twenty warriors in the assault ram. Saduran shouted the words, but behind his eyes his soul was silent. He heard the clink of mirror-coins and kill talismans against armour and weapon cases.