Event · M31
The Rubric of Ahriman
The Rubric of Ahriman was a sorcerous working cast by Ahzek Ahriman that transformed most Thousand Sons warriors into inert, dust-filled suits of armour. The ritual was undertaken to arrest the Flesh-Change, a degenerative mutation afflicting the Legion following the destruction of Prospero and the loss of the Emperor’s warding influence. Ahriman drew upon the accumulated sorcerous knowledge of the Thousand Sons and the assistance of loyal Rubricae-to-be in preparing the working, which he cast with or without the sanction of Magnus the Red, depending upon the account. The casting reduced the bulk of the Legion’s fighting strength to animate but soulless Rubric Marines, preserved the small cadre of surviving sorcerers with their minds intact, and led to Ahriman’s exile from the Legion; its consequences have shaped the Thousand Sons’ composition and character into the era of the Great Rift.
See where The Rubric of Ahriman occurred on the galactic map during the Horus Heresy.