The Thousand Sons are one of the most iconic and tragic Chaos Space Marine Legions in Warhammer 40K, dedicated to Tzeentch, the Chaos God of change, magic, and manipulation. Originally the XV Legion of the Legiones Astartes, the Thousand Sons were once loyal warriors of the Imperium, revered for their advanced knowledge of sorcery and the arcane. However, during the Horus Heresy, they fell victim to the schemes of Tzeentch, leading to their eventual corruption and damnation. Their downfall began with the Rubric of Ahriman, a disastrous ritual intended to save the Legion from mutating and dying due to a psychic curse, but instead transformed them into the dust-bound horrors they are now—cursed to wear their ancient armor and bound to the service of the Chaos God.