‘Kai is not a novitiate,’ said Athena.

‘Really?’ snapped Gregoras, rounding on Athena. ‘Yet he is quartered with them, and I am given to believe that he can no longer employ the nuncio. Nor is he capable of sending or receiving astro-telepathic communion. He is fit only for the hollow mountain. Am I incorrect in any of these statements?’

‘As a matter of fact, you are,’ said Athena. ‘Kai has a long way to go before he is fully recovered from the incident on the Argo, but his abilities return with every passing day. I will have him back in the mindhalls before long, you can be sure of that.’

A surge of gratitude washed through Kai as Athena spoke in his defence. They had known each other for a short time only, and though their initial meeting hadn’t exactly been a roaring success, their shared damage had at least established a common ground between them. Gregoras sensed her protectiveness and sat back with a slight smile playing around his thin lips. The cryptaesthesian took a shallow breath and brushed a piece of lint from his robe before opening the book in his lap.

‘A cognoscynth is a powerful psyker indeed, one with a very distinct modus operandi,’ said Gregoras. ‘It would be hard for one to use his abilities on Terra without at least one operative of the City of Sight being aware of it.’

‘So you don’t believe me?’ asked Kai.

‘Let us say I maintain a healthy degree of scepticism,’ replied Gregoras, ‘but I will indulge your delusion for the moment and tell you of the cognoscynths.’

HALFWAY ACROSS THE galaxy, two men met in a glittering cave, far beneath the paradise world they called home. The walls of the cave sang with unheard harmonies, the music of a world alive with the background hum of latent psychic powers bubbling beneath the surface of the planet’s consciousness.

One of the men was a giant, a towering figure robed in white and bearing a heavy leather book hung with small thurible and parchment strips. His name was Ahzek Ahriman, and among mortal men he was a demi-god, a figure of such awesome power and intellect that few of Terra’s greatest minds could match him in contests of wit and knowledge. His face was downcast as he stared at the second figure sitting cross-legged on the rocky floor at the exact centre of the cave.

Though Ahriman was a giant, the seated figure was even bigger. Likewise robed in white, he was a strange individual, with skin like burnished bronze and a mane of crimson hair like that of a furious lion.

On this world, at this time, there could be only one individual that gathered the light and power of the cave into himself.

Magnus the Red. The Crimson King, Primarch of the Thousand Sons and Master of Prospero.

None who knew the primarch would ever give identical descriptions of his face, attribute the same colour to his eyes, or give the same impression of his humours. Inconstant as the wind or the ocean waves, no two aspects of Magnus could ever be the same, and the light from the glittering crystals carried by the hundreds of thralls around the edges of the cave was both reflected and absorbed by his skin.

A faint shimmer of illumination connected Magnus to a strange device hanging from the cavern’s ceiling. Shaped like a giant telescope, its surfaces were carved with sigils unknown beyond this world, and silver vanes projected from a platinum rim around a giant green crystal at its centre.

For two nights Magnus had meditated, and for many more he had sat motionless beneath the bronze device as his acolyte read passages from the book in a never-ending recitation of formulae, incantations and numerical algorithms.

Had any of the polymaths of Terra been present, they would have wept at the beautiful complexity and lyrical simplicity of these equations. Devised by Magnus over decades of research and study, they were unique and known only to the Thousand Sons. A lifetime’s worth of irreplaceable knowledge was bound within the pages of the book carried by Ahriman, and its incalculable value was beyond imagining.

The Chief Librarian of the Thousand Sons had not faltered in his reading, every complex syllable voiced with a perfection that would have made the most demanding captain of the Emperor’s Children proud. He watched over Magnus with a son’s love for his father, and though he believed in his primarch’s genius and wisdom, he could not disguise the unease he felt at what they attempted here.

Magnus had not moved in four days, his subtle body crossing the unremembered and unknown reaches of the immaterium en route to a fateful meeting.

In his heart Magnus carried a warning for his father’s Imperium, but in his actions he carried the seeds of its doom.

GREGORAS TURNED THE book in his lap around to face them, and Kai saw a colour plate spread over two pages depicting a scene of battle. Yet this was no ordinary contest of arms, it was a conflict between warring soldiers of Old Earth, fought beneath a raging, bilious sky that split apart with shards of lightning and grotesque faces pressing through the clouds. A leering sun bathed the scene with a hellish light, and the faces of the combatants were twisted, not in hate, but in terror and anguish.

‘ Sargon of Akkad at the Gates of Uruk,’ said Kai, reading the caption beneath the picture. ‘I can’t say I’ve heard of this battle.’

‘Unsurprising,’ said Gregoras, ‘though I presume you will have heard of the psi-wars?’

Kai nodded. Athena nodded.

‘Of course you have, you would be ignorant psykers indeed had you not. Truth be told, little is known of those global wars with any certainty, just fragments culled from surviving records that escaped the purges of its aftermath. We believe they began, as all wars do, with ambition and greed, but it soon became clear that the warrior kings at each others throats were being directed by the will of power-mad individuals hidden in the shadows.’

‘The cognoscynths?’ asked Kai.

Gregoras nodded. ‘Psykers are an uncommon mutation. Perhaps one child in a million may be born with some latent power. And of those children, perhaps a tenth will have power worth harnessing. The gene-code for the cognoscynth is two orders of magnitude rarer. Now I want you to understand what that means, for it is not just a hyperbolic phrase. Cognoscynths are considerably rarer than any normal psyker, so to have so many arise on Old Earth at once was an event so singular as to demand its own named epoch. Yet no such epoch exists in the records, for some times are best forgotten.’

Kai had heard a bowdlerised version of the early years of the psi-wars, but his knowledge was sketchy at best. That period of psyker history was not well taught at the City of Sight. No one wanted to remember a time where psychic powers almost destroyed the world, least of all the psykers themselves.

‘Eventually it came to light that the great states of the world were simply pawns for powerful individuals who set nation against nation for their own savage amusement. No normal telepath could have done this, only one with the unique power of a cognoscynth.’

‘Why would anyone want to do that?’

Gregoras shrugged, but said, ‘You know the lure of psychic powers, Zulane. Despite the dangers, every astropath acquires a taste for using their powers. Once your mind touches the immaterium, it craves that wellspring of limitless potential like nothing else. Do you remember the first time you used your powers?’

‘Yes,’ said Kai, ‘it was intoxicating.’

‘Mistress Diyos?’

‘My mind could reach across the heavens, and I felt as though I was part of the fabric of the universe itself,’ said Athena.

‘Indeed, but no matter how many times you achieve communion after that first time, it is never quite the same,’ said Gregoras. ‘Every communion is dangerous, but you still willingly hurl your mind into a realm of terrible danger just to feel that rush of its power again.’