A vista of unsurpassed beauty lay before him, towering snow-capped mountains draped in a shawl of pine and fir, magnificent swathes of emerald green forests as far as the eye could see and a wide river of foaming, icy water. Hundreds of shaggy coated herbivores grazed on the plain and wide pinioned birds circled noisily overhead. Horus sat on the low slopes of the foothills at the base of the mountains, the sun warming his face and the grass wondrously soft beneath him.

'To hell with this,' he said as he got to his feet. 'I know I'm not dead, so what's going on?'

Once again, no one answered him, though this time he had expected an answer. The world still smelled sweet and fragrant, but with the memory of his identity came the knowledge of its falsehood. None of this was real, not the mountains or the river or the forests that covered the landscape, though there was something oddly familiar to it.

He remembered the dark, iron backdrop that lay behind this illusion and found that if he willed it, he could see the suggestion of that nightmarish vision behind the beauty of the world laid out before him.

Horus remembered thinking - a lifetime ago, it seemed - that perhaps this place might have been some netherworld between heaven and hell, but now laughed at the idea. He had long ago accepted the principle that the universe was simply matter, and that which was not matter was nothing. The universe was everything, and therefore nothing could exist beyond it.

Horus had the wit to see why some ancient theologian had claimed that the warp was, in fact, hell. He understood the reasoning, but he knew that the Empyrean was no metaphysical dimension, it was simply an echo of the material world, where random vortices of energy and strange breeds of malign xenos creatures made their homes.

As pleasing an axiom as that was, it still didn't answer the question of where he was.

How had he come to this place? His last memory was of speaking to Petronella Vivar in the apothecarion, telling her of his life, his hopes, his disappointments and his fears for the galaxy - conscious that he had told her those incendiary things as his valediction.

He couldn't change that, but he would damn well get to the bottom of what was happening to him now. Was it a fever dream brought on by whatever had wounded him? Had Temba's sword been poisoned? He dismissed that thought immediately, no poison could lay him low. Surveying his surroundings, he could see no sign of the wolves that had chased him through the dark forests, but suddenly remembered a familiar form that had ghosted behind the face of the pack leader. For the briefest instant, it had looked like Magnus, but surely he was back on Prospero licking his wounds after the Council of Nikaeal?

Something had happened to Horus on Davin's moon, but he had no idea what. His shoulder ached and he rotated it within his armour to loosen the muscle, but the motion served only to further aggravate it. Horus set off in the direction of the river once more, still thirsty despite knowing that he walked in an illusory realm.

Cresting the rise that then began to slope gently down towards the river, Horus pulled up sharply as he saw something startling: an armoured Astartes warrior floating face down in the water. Wedged in the shallows of the riverbank, the body rose and fell with the swell of the water, and Horus swiftly made his way towards it.

He splashed into the river and gripped the edges of the figure's shoulder guards, turning the body over with a heavy splash.

Horus gasped, seeing that the man was alive, and that it was someone he knew.

A beautiful man was how Loken had described him, a beautiful man who had been adored by all who knew him. The noblest hero of the Great Crusade had been another of his epithets.

Hastur Sejanus.

Loken marched away from the temple, angry at what his brothers had done and furious with himself: he should have known that Erebus would have had plans beyond the simple murder of the Warmaster.

His veins surged with the need to do violence, but Erebus was not here, and no one could tell Loken where he was. Torgaddon and Vipus marched alongside him, and even through his anger, Loken could sense his friends' astonishment at what had happened before the great gate of the Delphos.

'Throne, what's happening here?' asked Vipus as they reached the top of the processional steps. 'Garvi, what's happening? Are the first captain and Little Horus our enemies now?'

Loken shook his head. 'No, Nero, they are our brothers, they are simply being used. As I think we all are.'

'By Erebus?' asked Torgaddon.

'Erebus?' said Vipus. 'What has he got to do with this?'

'Garviel thinks that Erebus is behind what's happening to the Warmaster,' said Torgaddon.

Loken shot him an exasperated stare.

'You're joking?'

'Not this time, Nero,' said Torgaddon.

'Tarik,' snapped Loken. 'Keep your voice down or everyone will hear.'

'So what if they do, Garvi?' hissed Torgaddon. 'If Erebus is behind this, then everyone should know about it: we should expose him.'

'And we will,' promised Loken, watching as the pinpricks of vehicle headlights appeared at the mouth of the valley they had only recently flown up.

'So what do we do?' asked Vipus.

That was the question, realised Loken. They needed more information before they could act, and they needed it now. He fought for calm so that he could think more clearly.

Loken wanted answers, but he had to know what questions to ask first, and there was one man who had always been able to cut through his confusion and steer him in the right direction.

Loken set off down the steps, heading back towards the Thunderhawk. Torgaddon, Vipus and the warriors of Locasta followed him. As he reached the bottom of the steps, he turned to them and said, 'I need you two to stay here. Keep an eye on the temple and make sure that nothing bad happens'

'Define "bad".' said Vipus.

'I'm not sure,' said Loken. 'Just… bad, you know? And contact me if you get so much as a glimpse of Erebus'

'Where are you going?' asked Torgaddon. 'I'm going back to the Vengeful Spirit! '

'What for?'

'To get some answers,' said Loken.

'Hastur!' cried Horus, reaching down to lift his fallen friend from the water. Sejanus was limp in his arms, though Horus could tell he lived by the pulse in his throat and the colour in his cheeks. Horus dragged Sejanus from the water, wondering if his presence might be another of the strange realm's illusions or if his old friend might in fact be a threat to him.

Sej anus's chest hiked convulsively as he brought up a lungful of water, and Horus rolled him onto his side, knowing that the genhanced physique of an Astartes warrior made it almost impossible for him to drown.

'Hastur, is it really you?' asked Horus, knowing that in this place, such a question was probably meaningless, but overcome with joy to see his beloved Sejanus again. He remembered the pain he had felt when his most favoured son had been hacked down upon the onyx floor of the false Emperor's palace on Sixty-Three Nineteen, and the Cthonic bellicosity that had demanded blood vengeance.

Sejanus heaved a last flood of water and propped himself up on his elbow, sucking great lungfuls of the clean air. His hand clutched at his throat as though searching for something, and he looked relieved to find that it wasn't there.

'My son,' said Horus as Sejanus turned towards him. He was exactly as Horus remembered him, perfect in every detail: the noble face, wide set eyes and firm, straight nose that could be a mirror for the Warmaster himself.

Any thoughts that Sejanus might be a threat to him were swept away as he saw the silver shine of his eyes and knew that this surely was Hastur Sejanus. How such a thing was possible was beyond him, but he did not question this miracle for fear that it might be snatched away from him.