Masters of Forbidden Knowledge
The Thousand Sons Space Marine Legion
The Thousand Sons were born of Magnus, the changeling Primarch. A physical giant possessed of coppery skin, fiery red hair and a single, baleful eye. Some say his massive size reflected his enmormous intellect; his cyclopean eye his single-minded strength of purpose. At the height of the Great Crusade, Magnus was amongst the most imposing of the Primarchs and was always the one most suspected of taint. He would endure the whispers of Chaos throughout his life...
Origins
When the Primarchs were mysteriously scattered from their incubation on Terra, the infant Magnus fell upon the remote colony world of Prospero. He could hardly have been more fortunate: a grotesque cyclopean mutant who might have been feared and shunned on any other world cam instead upon a hidden planet of kindred spirits: a commune of outcast human psykers. It would not be the last time Magnus's destiny would be so conveniently manipulated.
The original settlers of Prospero had chosen the world for its remoteness from Terra and had gone to great lengths to sever contact with Humanity. Their single citadel was situated deep in the planet's ventral mountain range. Nourished by vast underground hydroponics for sustenance and techno-psychic collector arrays for sustainable energy, it was a construct of extraordinary beauty. The so-called 'City of Light' glittered amidst the desolation of Prospero, all gleaming silver towers, soaring obelisks and majestic pyramids. Within this carefully-artificed reclusium, far from the sight of Man, its commune of human refugees devoted themselves completely to the pursuit of knowledge and the mastery of the nascent mutation which had set them apart: their developing psychic powers.
Legend tells of Magnus arriving like a portentous comet, streaking through the thin atmosphere of Prospero and coming to rest in the central plaza of the city. The vulnerability of their sanctuary to approach from above was something the adepts of Prospero failed to recognize: a failure for which they would suffer greatly in times to come.
Magnus became a ward of the scholars of the commune. Perhaps they recognized their kinship in a mutant cast out among mutants. Perhaps they recognized his potential. What is known is how quickly the young Primarch himself began to manifest the sort of powers which had caused his mentors to flee into isolationl and how utterly he brought those powers under his control. Magnus mastered every psychic discipline, quickly surpassing the abilities of the greatest adepts in the commune. By the time he approached physical maturity, Magnus had grown into a giant in the psychic and intellectual, as well as the physical, sense. Then came the day that Magnus opened his cyclopean eye upon the Empyrean, and instead of channeling power from the Warp, Magnus instead saw into it, and life on Prospero was changed forever.
The instant his single enormous eye saw into that place of power, Magnus the Red went from student to absolute master.
The Warp is no more a lifeless place than the physical world, and the arrival of so prodigious a psychic presence as Magnus did not go unnoticed. More than one consciousness sensed the new life across the Immaterium and more than one recognized him for who he was.
More than one came to find him.
The Apocrypha of Skaros records the day the Emperor and his host arrived upon Prospero.
'It was as though they were friends of old; of many years acquaintance. Magnus's mutant visage disturbed not the Emperor of Man, who embraced his lost Primarch and proclaimed him his own'
The Emperor had chosen as his vanguard force for the expedition his fifteenth Legion, the Space Marines progeny infused with Magnus's own gene-seed. The Apocrypha records the moment Primarch and Legion were united.
'The Warp-lost Primarch heard his Emperor and spoke but a simple response, "As I am your son, they shall become mine." Then he knelt and in that moment accepted Primacy of the fifteenth Legion: his Thousand Sons.'
The discovery of their lost master could not have come soner for the Thousand Sons. Formed from Magnus's own gene-seed, the Legion was disposed toward psychic mutancy in disproportionate numbers; a circumstance the fledgling Imperium was ill equipped to handle. Deep factionalism divided those who recognized the benefit of stable mutations such as the so-called 'Navigator Gene' of the Navis Nobilite. The Navigator Houses' 'third eye' allowed them to steer a course through the Immaterium making warp travel possible, but some perceived the increasing and seemingly random nature of human mutation as a destructive internal threat. An entire Legion of potential mutants was seen as a dangerous development. The fifteenth Legion had suffered terribly from the spontaneous, uncontrolled manifestation of psychics amongst their ranks, and those who survived to receive training became amongst the most powerful librarians of the epoch. Many more did not. Moreover, the increasingly vocal anti-mutant 'witch hunting' crusades within the Imperium had seized upon the out-of-control Legion as evidence of the danger of psychic mutation. Cries that demanded purging the Imperium of psykers completely were not uncommon, and those directed at the remote and superhuman Space Marines of the Thousand Sons were amongst the most strident. Magnus came just in time to save the Legion from the threat of destruction. Relocating its entire depleted strength to Prospero, Magnus turned the might of his intellect to their instruction in the ways of the psyker.
There are scholars, especially among the Librarians of certain Space Marine Chapters, who suggest it was during this time that another threshold was crossed. They believe that the crisis of controlling an entire Legion's destructive psychic mutancy caused Magnus to seek shortcuts, or explore more perilous paths. There are others, including prominent members of the Inquisition, who suggest no such 'threshold' ever existed; that the original commune of psychic adepts were already students of darker arts before Magnus came amongst them. Thus his initiation into similar rites was inevitable. Still others postulate it was the magnitude of the Primarch's own insatiable hunger for knowledge that made what followed inevitiable. When it happened will never be known, but at some point, Magnus the Red and his Thousand Sons Legion pursued knowledge beyond scholarship and psychic discipline, and began to practice sorcery.
The difference was not universally noticed at first. Magnus joined the Great Crusade with vigour. He led the Thousand Sons alongside the Emperor, the other rediscovered Primarchs with their Legions and all the fighting forces of Man. They fought in a grand campaign radiated outward from Terra, liberating colonies long isolated and claiming new worlds for the glory of the Emperor. That the Thousand Sons accomplished their victories through guile and deception as often as by strength of arms did not initially draw concern. Victory was victory after all. However, the further the Emperor's realm expanded, the more tenacious grew the opposition. Increasingly, Legions of Space Marines or regiments of Imperial Guard would make planetfall expecting to find lost colonies of men, only to discover the thralls of mysterious powers utterly inimical to them. These slave cults resisted with daemonic beings from across the Warp, powers few could fail to notice were akin to those weilded by the Thousand Sons of Magnus. There were those amongst the Imperial court suspicious of the Thousand Sons' methods. Paramount amongst them was Mortarion, sepulchral lord of the Death Guard who knew too well from his own dark past that sorcerous power never came without a price. Leman Russ, Primarch of the Space Wolves, for whom any battle fought through sleight of hand and clever deceit was by definition dishonorable also lent his voice to the critics of the Thousand Sons. The schism grew so great that it threatened the very foundations of the new order, and so the Emperor of Man himself decreed a council to resolve the issue for all time. The mightiest proponents of both sides convened on the planet Nikaea to debate, with the Emperor himself enthroned above the dais as arbiter, in an ancient amphitheater that seated tens of thousands. There, beneath the glittering starlight, the witch hunters presented their case. They recited a litany of human misery inflicted upon the Emperor's own subjects by sorcerers enslaved by Chaotic monstrosities; of mutants unable to control what they had become, and despots who turned their psychic gifts to dark and selfish purpose. To speak against these charges came Magnus himself. He climbed the dais in silence, his own visage seeming to confirm everything the witch hunters asserted. But when he began to speak, it was clear none of his accusers could match the charisma or presence of a Space Marines Primarch and least of all this particular Primarch's certainty of conviction. Magnus told the assembled throng that no knowledge was tainted of itself, and no pursuit of knowledge ever wrong so long as the seeker of that truth was master of what he learned. And, Magnus decreed with finality, there were no secrets the Thousand Sons had not mastered, no ways too labyrinthine for them to know. When he stepped from the dais, the council was divided more sharply than ever: the witch hunters had made their case collectively with great impact, but with insufficient power to blunt the persuasiveness of the Primarch of the Thousand Sons. The assemblage openly wondered if even the Emperor could decide against one of his own sons.
The tension had reached the palpable knife-edge of violence when a contingent of Space Marine Librarians approached the dais. The Emperor acknowledged them with a nod and all fell silent, for visible amonst the librarians were the chiefs of some of the greatest Legions in the Imperium. These mystic warriors formed a semicircle about he podium to indicate they spoke with one voice, but it was a young Epistolary who stepped forward to deliver their words. Though his identity has been lost to history, he is said to have spoken with a passion that bordered on ferocity, and offered to the assembled council a third alternative. A psyker, he proposed, like an athlete, was a gifted individual whose native talent must be carefully nurtured. Psykers were not evil in themselves. Sorcery was a knowledge that had to be sought, even bargained for, and neither man nor paragon could be certain they had the best of such bargains. The other Librarians united around him, and proposed that the education of human psykers to best serve Mankind be made an Imperial priority. The conduct of sorcery would be outlawed forevermore as an unforgivable heresy against Mankind.
The compromise presented by the Librarians offered both factions something, and appeared to be what the Emperor himself had been waiting for. The Emperor ruled it law without allowing any rebuttal, and the Edicts of Nikaea stand to this millennium as Imperial policy regarding human psychic mutation. But it was not the decision favored by Magnus. The Grimoire Hereticus records the fateful face-to-face confrontation between father and son when the Emperor himself barred Magnus's attempt to storm from the hall in protest. He bade Magnus cease the practice of sorcery and incantation, and the pursuit of all knowledge related to magic. It is said the cyclopean Primarch's face appeared brittle as aged stone as he received his father's command. Brittle enough to crack, but the Primarch of the Thousand Sons bent his shoulder and pledged himself and his Legion to obey. Neither Emperor not Primarch knew that this moment would be the last time they would meet, and that events had been set in motion that would climax in treachery, bloodshed and pain. Taken from White Dwarf 266US