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 enormous 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...


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 came 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 pla/a of the city. The vulnerability of their sanctuary to approach from above was something the adepts of Prospero failed to recognise: a failure for which they would suffer greatly in times to come.

Magnus became a ward of the scholars of the commune. Perhaps they recognised their kinship in a mutant cast out among mutants. Perhaps they recognised 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 isolation; 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 channelling 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 recognised 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 ot 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.'

It has been suggested that the face-to-face meeting of Emperor and Primarch was a virtual afterthought, their minds having long since found each other across the Warp.

The Emperor had chosen as his vanguard force for the expedition his fifteenth Legion, the Space Marine 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 sooner 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 recognised 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 among 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 inevitable. 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 radiating 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 sorcerous powers granted them by daemonic beings from across the Warp, powers few could fail to notice were akin to those wielded 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 dishonourable 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 amphitheatre 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 amongst the librarians were the chiefs of some of the greatest Legions in the Imperium. These mystic warriors formed a semicircle about the 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 favoured 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 nor 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.

The Betrayal

The threat to the fledgling Imperium resolved by the council served to mask other, darker betrayals already in motion. On Davin, events were reaching their tragic climax as Horus, first among equals, Warmaster and right arm of the Emperor fell victim to the manipulations of Chaos. This threat would not be resolved by debate or decree. Enthralled completely by the dark powers, Horus emerged from the events on Davin intent on nothing less than the complete destruction of the Imperium. Suborning brother Primarchs and their Legions to join his own, Horus intended to take the rest of the Imperium and indeed the Emperor himself by complete surprise. He was a brilliant strategist; he believed he had manipulated every possible factor to ensure his success. He had miscalculated in only one regard. Despite the decree of his Father and despite his own sworn promise, Magnus had not turned from the pursuit of the dark arts.

Seeing into the depths of the Warp from his sanctum upon Prospero, Magnus beheld a vision of Horus' pledge of fealty to Chaos upon the fields of the feral world of Davin. Horus' treachery was revealed, every detail made known with total clarity. Magnus saw the too-human foibles of Fulgrim of the Emperor's Children and Angron of the World Eaters played upon masterfully by Horus, and greater forces veiled by the Warp. He saw the terrible trap being laid for Ferrus Manus of the Iron Hands, Vulkan of the Salamanders and cautious Corax of the Raven Guard on Istvaan V. He saw the Emperor's mightiest bastion of unalloyed loyalty, Guilliman's Ultramarines, being cleverly decoyed to the far side of the galaxy, where they could play little part in the drama to unfold. Alone in the entire galaxy, more clearly than even Horus himself, Magnus was given to understand the events at hand. He saw it all and understood each consequence and every role, except his own.

There are generals, tacticians and great military minds who say that had Magnus acted upon his knowledge and taken ship with his Thousand Sons he could have changed the course of the Heresy. Others point out that the Warp is an imprecise place, and Magnus could not be sure he would arrive in time to prevent Horus's treachery. Instead of direct intervention, Magnus embarked upon a more perilous path. The Primarch had never accepted the Emperor's belief in the peril of sorcery, and had broken his oath to turn from the pursuit of such knowledge.

In his precognitive vision of the coming war, and the warning it provided, Magnus was certain he had found proof of the value of his studies. With the combined power of his fellow sorcerers he set about casting a spell across time and space. Breaching all the protective hexes and wards of the Imperial Palace on Terra, he projected his warning of impending revolution into the presence of the Emperor himself, naming Warmaster Horus as its chief architect.

It was to be his moment of triumph and vindication, the occasion of his self-righteous justification. Only the power of Magnus's sorcery had revealed the viper within. Surely the Emperor would at last see its value. Instead, the Emperor named Magnus's sorceries themselves as the viper. He judged Magnus's accusation of his brother Primarch heretical and his blatant deception evidence of the worst sort of oath breaking. Magnus's pursuit of forbidden knowledge was deemed tragic proof that he had fallen under the sway of the very powers the Emperor had warned him against. The Emperor's worst fears for the soul of his cyclopean son had been realised.

The content of Magnus's warning was ignored completely. It is said the Emperor broke contact with such force that psychic wards throughout the Palace arced with lightning and shattered. At the Emperor's side stood Russ, quaking with barely-contained wrath at Magnus's actions. The Emperor turned to him, for he knew he could be counted upon to prosecute his next orders without restraint. He ordered the Space Wolves to be unleashed upon Magnus and the scholar-soldiers of Prospero.

Only those who witnessed those distant days will ever truly know what happened upon Prospero when the Space Wolves attacked, as extant accounts often contradict each other dramatically. The epic, 'Prospero's Lament', describes a lengthy orbital bombardment by the Space Wolves, followed by a systematic campaign across the planet that took many days and nights, with a death toll of horrific proportions on both sides. On the other hand, one of the Space Wolves' strongest oral accounts of the battle, The Edda of the Hammer', asserts the Space Wolves took the Thousand Sons completely by surprise. The Space Wolves fell upon the City of Light from above (as Magnus had, so many years before) and reduced it in one terrible, bloody night of violence and carnage. The single night of burning libraries, crashing towers and feral mayhem is a potent image and the action described in the Edda matches the popular image of the Space Wolves. But the Edda is oft-criticised; for how could a planet of sorcerers, able to see across time and space and into the future, be so completely surprised as to face destruction in the course of a single night? How indeed, unless the dark powers which granted them their visions did not mean for them to see? However it occurred, the sack of Prospero was the ultimate horror for the scholarly Thousand Sons, as Russ and his Space Wolves smashed their way through the sanctuary of the City of Light. Russ's warriors built pyres from Magnus's libraries of books, parchments and ancient texts, destroying artifacts unique in all the galaxy with a stroke of the chainsword. Though they differ in their specifics, most accounts suggest Magnus himself met Leman Russ in hand-to-hand combat, Primarch against Primarch, berserker against giant in the ruined heart of the City. The War of the Giants', committed to print by Inquisitor Bastalek Grim from Space Wolf oral tradition, describes the titanic duel that followed:

'Magnus the Red did take to the field of battle, causing the ravaged ground to liquefy 'neath his mighty stride. Russ charged bodily the crimson behemoth and did lift the Cyclops off the ground, The Wolf-King broke the back of the Cyclops, and the last Thousand Sons, seeing their Primarch broken and cast down, did turn and flee. But as Russ raised Frostblade Mjalnar to deliver the killing blow, Magnus spoke a word ot power, and did sink away into the iridescent ground.'

In accounting what took place at the last, claims of what occurred on Prospero's final night contradict wildly. Somehow, in the City of Light's dying moments, Magnus cheated Russ of total victory, and in so doing, paid the very price the Emperor had warned him against all along.

Everything that mattered to him was burning to the ground, and Magnus turned to what he knew best to save it. Magnus was swept upon the currents of the Warp, and there he found the knowledge he sought. His sorcerers, his beloved Legion, all the precious knowledge they had accumulated within the silver spires of the City of Light could still be saved. He discovered the solution looking back at him, as if it had always been there, watching his way, and subtly changing him to its own purpose. He beheld sorcery incarnate, promising knowledge, power and salvation. But this time it was on its own terms. Magnus was no longer the master of the way as he had believed himself, but servant to it. It is said that even then Magnus hesitated, but as he thought back to his city, his works, his knowledge and his brethren, reduced to fiery ruin at the command of his own father, he changed his allegiance for all time.

And in that instant, the City of Light, its silver towers and vast libraries and its Legion of Thousand Sons vanished from the face of Prospero, and the Imperium, forever. When Magnus and his Thousand Sons were seen again, it was above Istvaan V, fighting alongside Horus. Magnus had become a Daemon Prince of the Chaos god Tzeentch, Lord of Sorcery, and Changer of the Ways. The battle for their souls and their fate now so complete, it leaves one wondering whether it was ever truly in doubt.

The Rubric of Ahriman

The Thousand Sons had nearly been destroyed by the threat of uncontrolled mutation in their earliest days before their reunion with their Primarch. Even the salvation presented by Magnus's instruction was imperfect, requiring constant and vigilant oversight. The terror of it never left some of the Legion's most veteran members, and the rampant corruption they beheld amongst other Traitor Legions as the Heresy ran its course appalled them. They dedicated themselves exclusively to their new master, and for a time Tzeentch seemed to shield them from a similar fate. Even when the Heresy ultimately failed, and the Thousand Sons were forced to fall back to the Eye of Terror with their comrades in rebellion, Tzeentch's favour seemed unilateral. Their patron god provided a new planet, rich in magical power for them, a haven from the madness within the Eye for them to continue their research. But the way of the Master of Sorcery is capricious, and no sooner were the Thousand Sons ensconced upon their new home world than the Changer of the Ways began to alter them. Grotesque mutations in images favoured by Tzeentch appeared spontaneously throughout the Legion. Many embraced these manifestations as tokens of their new destiny, but to the senior members of the Legion it was as if all they had been through counted for nothing. All their sacrifices; the loss of Prospero, the bloodshed of the Heresy, all was rendered meaningless. Their valiant pursuit of knowledge had resulted in the very madness and abomination they had always feared.

An inner cabal of the mightiest sorcerers, led by their Chief Librarian and Magnus's most trusted advisor, Ahriman, determined to counter the warping corruption. They laid the foundations of a mighty spell, and protected their workings with wards of secrecy, for they doubted Magnus would bless so risky an enterprise. They would dispel the violent mutations washing over their battle brothers and render the Thousand Sons immune to the warping effects of Chaos. The Grimoire Hereticus describes a spell of such unimaginable power that even daemonic horrors fled before the singular roaring maelstrom of magic unleashed by Ahriman and his cabal. The Planet of Sorcerers was enveloped in impenetrable storms of blue and yellow lightning, forks of the titanic energy arcing across the planet to strike down corrupted Thousand Sons one after another until it is said Magnus himself was forced to intervene.

The aftermath was nothing like what the cabal had hoped for. Across the breadth of the world, the fighting strength of the Thousand Sons Legion had in a single stroke been destroyed utterly - and preserved for eternity. The reviled mutations were no more, because the flesh of the affected Space Marines had been reduced to dust, sealed forever* inside armour mystically welded shut. Every clasp, joint and seam had been sealed as though by infernal fire, trapping the animate spirit of the Thousand Sons irrecoverably within. Virtually the entirety of Magnus's Legion had been transformed into little more than implacable automata for all time, Magnus was enraged. The Legion he had sacrificed everything for was no more. The pursuit of knowledge that had always been foremost to each of his brethren was now denied them for all time. By their own hand, the majority of this Legion of scholars could no longer even think.

Everything he had done, all he had sacrificed, every critical decision he had made in his life had been founded upon two sacred beliefs: that knowledge was pure, and that he was its master. With his home world destroyed, his father his sworn enemy, and his Legion in ruin, Magnus of the Thousand Sons ascended his tower in despair. Casting his bitter gaze out upon the war-weary and fragile Imperium of Man, Magnus vowed, as Horus had at the height of the Heresy, that he would see the galaxy burn.

Home World

Prospero was chosen by its original settlers for one reason: its remoteness. Isolated from the most common Imperial travel lanes and boasting virtually no independent resources of any value, Prospero had only one redeeming quality: it was a good place to hide. In the end, it was not even that. Today it is a blasted ruin, declared Purgatus by the Inquisition.

Through the millennia of endless raiding since, it has been discerned the City of Light survived its transit through the Immaterium intact. It came to rest within the Eye of Terror, upon a world that has come to be known as the Planet of Sorcerers. That daemonic place is a seething cauldron of magical power, reflected across its breadth in the form of infernal volcanism and tempestuous skies saturated with magical vapour. Towers jut from craggy fists of rock thrust up from plains of lava, twisted and obscene mockeries of the spires and pyramids of learning which were the hallmarks of the City of Light before its fall. Mightiest of them all is the obsidian monolith that is the Tower of the Cyclops, said to be so massive it can be discerned from space with the naked eye. More obscenely, the Tower of the Cyclops looks back, as the pinnacle of the obelisk is a glowing warp eye, through which Magnus watches the paths of the future. The Silver Towers of the City of Light have been transfigured by the sorcerous might of the Thousand Sons into space-faring fortresses in which psyker lords set out from the Planet of Sorcerers to traverse the cosmos, launching vengeful assaults upon the Imperium of Man.

Combat Doctrine

The Thousand Sons were well known for preferring to avoid close combat, instead relying upon their mastery of psychic power and sorcery to carry the day. Guile, feint, confusion and misdirection were their hallmarks; all stratagems better used at range. Many were the occasions a Thousand Sons detachment would accomplish through illusion or trickery what a brother Legion would pay for dearly in blood.

Whatever else it may have changed, the Rubric of Ahriman affected that doctrine very little. The sorcerer lords of the Thousand Sons still use their ghost-brethren as implacable bulwarks of gunfire, around which they construct elaborate plans of guile and misdirection to achieve victory, all driven home with a timely application of potent magic.


Magnus placed great faith in his subordinates, believing he had taught them well, that their powerful sorceries gave them the necessary tools to function independent of him. Before the Heresy, individual Thousand Sons squads were not led by veteran sergeants but by those who showed the most psychic promise. These 'thrall-wizards' were apprenticed to more experienced sorcerers for their cabalistic training, but at the same time gained experience leading men in small units. While this practice meant it was rare for a Thousand Son who did not possess some measure of psychic talent to become a ranking officer, it also meant those sorcerers who did gain prominence had considerable combat experience. As a result, the Thousand Sons, a numerically small Legion to begin with, rarely took to the field en masse. Instead they campaigned in smaller detachments under the command of sorcerers who often acted with much more authority independent of their Primarch than the officers of other Legions. This command experience has stood them in good stead as independent leaders of warbands since the Heresy, to the Imperium's considerable and continuing misfortune.


For the Primarch Magnus, knowledge was power. He believed there was no discipline his intellect could not master, no secret he could not unlock and make serve his purpose. For the Thousand Sons, knowledge was salvation, the means to controlling the psychic legacy of their Primarch's gene. Every book was sacred, every writing worthy of study, every document a resource to be drained. The ultimate knowledge was sorcery, the way to final enlightenment, the key to the universe. Before the Heresy, the Thousand Sons were publicly dogmatic, swearing oaths of loyalty and singing the Imperial hymns. They fought for the expansion of the Emperor's realm with diligence, but as their oath-breaking illustrated, their final loyalty rested not with the Emperor, but with their Primarch. When Magnus's reach for intellectual mastery exceeded his grasp, Tzeentch was waiting for him, and the Space Marines who believed as he did could do nothing but fall with him.


Magnus was unquestionably the most profoundly mutated of the Emperor's Primarchs, both physically and psychically, and the Legion imprinted with his gene-seed reflected that with a high percentage of Thousand Sons manifesting some level of psychic ability. Early in the Legion's history a small, but significant percentage were prone to physical mutation, but in the wake of falling thrall to Tzeentch that percentage escalated wildly. The Rubric ended that forever for the battle brothers of the Thousand Sons, but the sorcerers who command those armoured shells still carry the gene-seed of their Daemon Prince, and wear their grotesque mutations proudly as tokens of their mercurial patron's favour.


A ghostly whisper of: "All is Dust!"