The figure before him was his father in every detail. He remained solid even as the cloister’s reality softened. Fragments of stone fell from the ceiling, onto the Emperor’s shoulders. He brushed them away. He looked up at the spreading cracks, then down at Sanguinius. The face of nobility became one of profound sadness. ‘Is that your belief?’ the Emperor asked.

‘It is.’

The ground trembled. The world swayed in the wind.

‘If you believe I am a lie,’ the Emperor said, ‘then it is clear what you must do.’ He took a step towards Sanguinius. He spread His arms, hands open. He lifted His head, exposing His throat.

Sanguinius gripped the hilt of the Blade Encarmine. He did not draw it yet.

This is the choice. This is the choice. This is the choice.

Will you kill the Emperor?

‘You must act on the truth,’ the Emperor said. ‘You cannot permit a lie to stand. Here I am. If I am a lie, strike me down. Do not hesitate.’

Sanguinius hesitated. The enormity of the act was too great. In the garden, the fountain of Baal toppled. The pillars were crumbling now. Sharp chunks of marble dropped from the arches, shattering against flagstones. The wind keened with grief.

The Emperor did not blur. His reality was strong. If anything, it became stronger as the cloister fell apart. How, Sanguinius wondered, could he be an illusion? The presence was not as he remembered his father, but it was a presence, more definite than any he had encountered since entering the portal. The bloody realities of Horus, so absolute when Sanguinius lived his death and his triumph, now seemed like pale simulacra. Perhaps it was Sanguinius’ memory of the Emperor that was faulty, blinding him to the truth in front of him.

The Emperor nodded. He lowered His arms. ‘Yes,’ He said. ‘We have all been blinded. Horus was. I was. You were, but are no longer.’ He smiled. ‘You do not strike the blow because you can see at last. You are making the choice, and it is the right one.’

There was a moment of gratitude. A moment of hope. A moment when the disintegration of the cloister stopped. Then Sanguinius tightened his grip on the Blade Encarmine. He drew the sword. The Emperor did not move. Sanguinius raised the Blade Encarmine high.

‘Will you kill me?’ the Emperor asked.