I see his pupils flicker, and can only guess at what scenes he is seeing. Like a prophet trapped in his own visions, Khârn is locked in a world of unreliable memory and paranoia. The damage done to his mind is heartbreaking. All that energy, all that raw potency, has been harnessed to an engine of lunacy.

Enough. It is time to show him how much I understand.

‘You didn’t come here for the Moon Wolf,’ I say, keeping my voice quiet. ‘You came here because you knew what devices once existed on Prospero. You hoped to find a cure.’

That halts him. He glares at me, and a fleck of spittle shines on his hanging lip like a jewel.

‘There is still time,’ I say, knowing the danger it places me in. I begin to wonder if this encounter was foreseen after all. ‘The devices have all been destroyed, but I can replicate their functions. I can heal your mind. I can remove the implants and give you back your sleep. I can take away the fire that drives you onwards, the fire that goads you to the acts you abhor. Even now, I know that a part of you still abhors what you have done.’

The spittle hangs, trembling, on his unmoving flesh.

‘I can help you, brother. I can heal your mind.’

He remains locked, frozen in indecision. If I had been Corvidae, I could have seen the paths of the future bisect within him, one going left, one going right. He is at the juncture now, what the ancients called crisis. He has the power to choose, to pull back or to plough on. I cannot intervene. The slightest nudge now will unleash the inferno, one that would toss me aside like dried brush in the hurricane.

I dare to believe in him for the space of a heartbeat. He looks at me, and I see the vindication of my guesses. He is lost in a universe of pain, one that is only temporarily forgotten in the action of killing. I know that my words have reached the sliver of his old self that still endures. I know he can hear me.

And so we remain, alone, locked away somewhere in the ruins of Prospero, a tiny mirror of the battle of wills taking place all across the galaxy.

And for that single heartbeat, I dare to believe.

‘Witch!’ he roars then, and the spittle flies from his lips. ‘ Youcannot heal this!’

Like a prey-beast springing away from the spear, he drags up a cry of tortured rage, shaking his head from side to side, flailing sweat from the bronze skin. He balls his massive fists, and I know they will come for me soon. His face contorts into a vice of bitter anguish, the expression that it will surely wear for millennia hence if I cannot stop him now.

He has chosen.

I cry aloud words of power, words I had forgotten existed until this moment. I am weak, crippled by the rigours of my captivity, but the lessons of my long conditioning are strong.

I am Athanaean, a master of the hidden ways of the mind, and there are more weapons in the galaxy than fists and blades.

My bonds shatter, freeing me to move. I rise from the chair, wreathed in the blazing light of the unbound aether, ignoring the protests of my broken limbs.

He comes at me then, the Eater of Worlds, and there is murder in his red-rimmed eyes. I have hurt him by exposing the source of his anguish, and I know then he will not stop until I lie dead and my blood paints every wall of this cell.

But we are on my world, the wellspring of my Legion’s ancient power, and the very dust of Tizca fuels my mastery of the warp. I am more powerful than he guesses.

He howls, this ruined abomination, as he thunders into strike-range. I meet the challenge, and my conscience is clear.

I cannot cure him, so I will have to kill him.

ARVIDA ARRIVED AT the landing site just in time.

Just in time to see the corpses of the pilots being dragged across the ground, leaving furrows in the sharp-edged dust. Just in time to see the krak-charges being laid around the flanks of the lander. Just in time to hear the rasping laughter of victory from the berserkers who’d stormed the vehicle.

There were twenty-seven World Eaters clustered around the empty crew-bay. One of them lay in the dust, his armour punched open from bolter impacts. The only other casualties were the two Thousand Sons who’d been left to guard it. They hadn’t stood much of a chance.

Arvida ducked down, keeping hidden behind a tangled hedge of semi-melted girders thirty metres away. As he watched, the helms of his brothers were torn off. Their exposed faces were punched, over and over again. The heads lolled lifelessly, turning into raw lumps of gore and gristle under the pointless barrage. The World Eaters laughed some more, cheering as each fist hit home.

Arvida turned away. He felt angry enough, but not towards Angron’s warriors – they were just savages, and had long ago ceased to be capable of anything more than boneheaded thuggery. His real anger was directed towards Kalliston, the one who had led them here against his counsel. The captain had always had too much faith in the providence of fate. The very idea that Magnus might have been fallible, that the primarch’s leadership might have been badly misguided, was anathema to him. Clearly it had been. They should have remained in space, searching for more survivors before heading into the emptiness of the void to recover. Prospero was nothing but a graveyard.

Even so, that left much to be explained. Arvida might have understood if there had been Wolves on Prospero, but World Eaters were another matter. Had the two Legions been acting in concert? Had all the other Legions turned against the Thousand Sons? If so, then why now? And for what reason?

The World Eaters began to strip the rest of the armour from their captives, and the desecration of their bodies began in earnest. Whoops and roars filled the otherwise tranquil air as they set to work.

Arvida glanced at his helm display. His squad were all gone, their life-signs inactive. He was alone, facing an enemy he couldn’t hope to contest.

The safest course of action would be to retreat, to flee back through the silent streets and wait for something to turn up. He knew he would have to withdraw soon enough, but the senseless barbarism in front of him offended his highly-developed sense of pride in the rules of war. His Legion had never broken them.

He rose from cover and drew his bolter up in a single, flowing movement. As he took aim, he saw the path of the shell that he would fire snaking into the future, and took some solace from the certainty of the kill. He squeezed the trigger, then turned and sprinted back into the shadows.

Arvida didn’t see the captain of the World Eaters collapse to the ground, his helm carved in two by the detonation of the bolt-round, but he heard it. Then he heard the roars of anger, and the thud of four dozen boots as the warband wheeled and charged towards the source of the shot.

He ran, keeping his head low, ducking and weaving through the thickets of blasted iron. The noise of the pursuit echoed in his ears, harsh and brutal. If they caught him, he’d be lucky to suffer a quick death.

Arvida upped the pace, pushing his body into a new burst of speed, barely noticing the skeletal buildings rush past in the night. He knew it had been reckless to fire that shot. Stupid, even.

But, and just for a moment, it had felt good.

HIS STRENGTH IS breathtaking. It is as if every aspect of the Legiones Astartes has been stripped away in favour of that single facet. His fists move in blurs of speed, backed up by the prodigious power of his massive body. He has no weapon, but that scarcely seems to matter. He is used to carving up his foes with his hands.

He is always attacking, always looking for the way in. I parry as best I can, holding him back by attacking his only vulnerable part. I see his mind now as it will become in the future – a cauldron of seething, perpetual violence. The brief window I had on another Khârn has closed, and the corrupted half is all that remains. I can hammer away at that, flexing my telepathic muscles as he flexes his unnaturally stimmed physical ones, though I fear my attacks have little bite.