Fabius Bile - Horus Heresy: During the Horus Heresy, Bile did not follow the path of his fellow battle-brothers in their worship of Slaanesh. Instead he distanced himself from his Legion and devoted himself to researching forbidden genetic engineering technology that would unlock the secrets behind the Emperor's creation of the primarchs and the Astartes.Following the Drop Site Massacre Fabius had explored the ancient choral conclaves on Isstvan V, scavenging knowledge left there by the Chaos-corrupted Warsingers of the Isstvan System.Fabius later joined several Emperor's Children commanders such as Lucius and Marius Vairosean in using extreme torture to exorcise the Daemon that had possessed Fulgrim in the wake of the Drop Site Massacre.At his primarch's demand, Fabius produced his first cloned primarch, creating a replica of Ferrus Manus, the primarch of the Iron Hands Legion and Fulgrim's greatest friend among his brothers, which Fulgrim tried to again convert to his cause. Every single time, the clone of Ferrus refused the offer just like the original man and Fulgrim killed him again in his rage. Fabius created multiple clones of Ferrus Manus, and each refused to join the Traitors' cause before Fulgrim slew him in a rage.Fabius proved vital for the Emperor's Children during the Heresy, reviving both Lord Commander Eidolon and Lucius at the demand of their primarch. As the war ground on, his experiments became more and more depraved, torturing captive Space Marines of both the Traitor and Loyalist Legions to give birth to his first generation of Terata, Enhanced Warriors who could prove physically stronger than even other Astartes but were prone to rampant mutation and mental instability.The events of the Heresy culminated in the Siege of Terra. The Emperor's Children, by this time a Traitor Legion fully under the sway of the Warmaster Horus, invaded Terra with Horus but took little direct part in the fighting around the Imperial Palace.Instead, they descended upon the civilian populations of Terra's Administratum; the mind-bogglingly complex infrastructure of clerks, bureaucrats, curators and menials whose efforts kept the lifeblood of the Imperium flowing. Whole dynasties of staid scribes and strata of haughty prefects were caught as they fled the war zone consuming their world. They were consumed in their turn.More than a million prisoners were rendered down under Bile's supervision and distilled into an array of stimulants and intoxicants for the Emperor's Children to ingest. It was the crowning depravity of their slide into the abyss, and it pleased their new master Slaanesh greatly.Perhaps it was at this time that Fabius Bile committed himself completely to the darkness. He was certainly foremost in the experimentation upon living prisoners, keeping them alive in their torment for solar weeks at a time and cataloguing every ghoulish result. Even amidst the carnage that followed the breaking of the Heresy, the Great Scouring, Bile's fascination was with life, not death.Bile guided the Emperor's Children ever further into the embrace of Slaanesh, the Dark Prince. His surgeries ensured that only one path was left to them; an eternal pursuit of sensual excess that has scarred the stars ever since. Yet Bile himself never underwent the surgeries he so thoroughly inflicted on his so-called brothers.