The Thousand Sons are a Traitor Space Marine Legion originally devoted to knowledge, psychic mastery, and the pursuit of enlightenment, hailing from the planet Prospero and led by the primarch Magnus the Red. Once loyal to the Imperium, their obsession with sorcery and the Warp led to their damnation. During the Horus Heresy, their fate was sealed when they were exiled and later embraced the Chaos God Tzeentch, the Changer of Ways. As punishment—or salvation—Magnus struck a pact with Tzeentch, seeking to preserve his Legion from the corruption and mutations that plagued other Chaos Marines. This resulted in the catastrophic Rubric of Ahriman, a ritual intended to stabilize the Legion’s rampant psychic energy. The spell backfired: while powerful sorcerers were elevated in power, the majority of the Legion—those without strong psychic ability—were turned into Rubrik Marines: mindless automatons sealed forever in their power armor, reduced to dust held together by sorcery. Now, Rubrik Marines serve as unfeeling, tireless soldiers under the command of their sorcerer-brethren, enacting arcane wars across time and reality, their green-glowing eyes burning with the trapped remnants of what they once were.