‘I did know the moment,’ Sanguinius continued before they could speak. ‘On Pyrrhan, that changed. In the manufactorum, I confronted visions of the future. In all of them but one, I died. That was my moment of decision. I could accept what I had long known, or reject it. I chose the vision where I lived, and we triumphed.’

Next to him, the clink of Curze’s manacles and chains ceased.

‘Why are we here?’ said the Lion. ‘You made your choice on Pyrrhan, and we made ours in orbit. No one except Horus made a decision on the soil of Davin. There is nothing here except the traces of what happened to him. If this altar had a purpose, it has served it. There are relics of tragedy on Davin. That is all.’

‘So it would seem,’ Sanguinius said. ‘The world is deserted. Too much dust has gathered. Too much has eroded. The system is enclosed by bone. Is it not extravagantly dead? As if gods were determined to convince us that there is nothing?’

‘None of this advances us strategically,’ said Guilliman. ‘We have come here, Sanguinius, and we have seen. I feel the weight of this place, but this is getting us no closer to Terra. There is an intruder in the system, and we have the bulk of our forces planetside. We must leave.’

Sanguinius shook his head. He was not going to be deflected now. Not when understanding was so close, not when he could finally lay claim to the hope that had been denied him for so very long. ‘The way to Terra is here, Roboute. In this chamber. I am sure of it. This is still a fulcrum. It…’

He stopped. His eyes snapped wide in awe. He understood what he had been arguing. He understood the full implications of his words. He understood that Pyrrhan had only been a prologue. ‘Fate can be altered here,’ he said. ‘This is where Horus’ destiny was created. It was not inevitable that he would come here. Don’t you see?’ he pleaded. ‘Our father was not blind. He could not foresee Davin, because here is where the future changes. Here is where we will change it.’

Revelation blazed. He saw all the threads of possibilities, the severed and the chosen. He saw the knots of fate, and how they choked or were undone. ‘I will!’ Sanguinius shouted. ‘I will change the future!’

And his words summoned light.

The Lion cursed. He and Guilliman stepped back from the altar, weapons in hand.

A vertical slit opened in the air before the north wall. It ran from the dome to the floor, thin as a las-beam, and as bright. A second tear grew horizontally from its centre, arcing halfway around the cylinder wall. Diagonal lines lashed out, forming a star. The tear widened, turning from star to sphere, burning with white light. Sanguinius stared into brilliance. He beheld the ferocious energy of life and possibility.