Planet of the Sorcerers - Origins: Magnus the Red and those few of the Thousand Sons Legion who survived the Fall of Prospero to the Imperial Censure Host led by Leman Russ and the Space Wolves were transported by the will and power of Tzeentch through the Warp to the Planet of the Sorcerers, which at the time was located in the Eye of Terror.There they discovered that the entirety of what had once been the capital city of Prospero, Tizca, the City of Light, had also been moved or replicated in its entirety by the will of the Changer of Ways. Its pyramids and citadels still contained every record and scrap of knowledge that the Thousand Sons had recovered from across the galaxy during the Great Crusade, and thus the Thousand Sons' most precious possession had been saved, though the price had been the ultimate damnation of their souls.Magnus had willingly sacrificed the flesh that had contained his essence when he called out to Tzeentch to save him from death at the hands of Leman Russ, and in so doing, had ascended to the more evolved form of a Daemon Prince, one free from the constraints of mortality and the limits of reality. He now appeared before his surviving sons as a large humanoid form wreathed in the light of stars and the power of infinite possibility, with brilliant wings of shimmering Warp fire. Magnus the Red had become the first of the Daemon Primarchs.Unfortunately, not long after their arrival on Sortiarius, the Thousand Sons themselves succumbed to the "gift" of their patron and true saviour from the Fall of Prospero, the Chaos God Tzeentch -- the full return of their aberrant genetic mutations, which threatened to turn all of the surviving Thousand Sons into mindless, gibbering Chaos Spawn. Appalled by the return of the dreaded Flesh-Change, Ahriman led a secret cabal of the most powerful Thousand Sons Sorcerer Librarians who had survived the Fall of Prospero and guided them in the invocation of a powerful Daemonic spell later known as the Rubric of Ahriman.The spell was successful, but its success came at a high price: those battle-brothers of the Legion who lacked psychic abilities were transformed into living automatons known as Rubric Marines -- the Rubricae. Their bodies were reduced to dust, and their souls were forever sealed within their suits of power armour -- every joint magically sealed, forever trapping the souls within in a nightmare existence of living death.The minority of Thousand Sons Astartes who did possess psychic abilities and so did not succumb to the Rubric soon found their psychic abilities increased to a tremendous degree by the power of the spell. The ritual also accomplished its goal, halting the dreaded mutations, both in the surviving sorcerers and their undead brethren.Magnus was enraged by Ahriman's audacious spell and what it had done to his sons, but was secretly pleased with the level of sorcerous knowledge the Legion had attained through their metamorphosis. Confronting the cabal who had carried out the Rubric, Magnus nearly slew Ahriman in his rage, but Tzeentch intervened personally, sparing Ahriman's life, for he had proven to be a useful pawn and a living exemplar of the power of change.Magnus exiled Ahriman and his remaining collaborators from the Planet of the Sorcerers and ordered them to forever roam the galaxy in search of understanding and knowledge of the true meaning of Chaos, a quest that continues unto the present day.