Horus Heresy - Schism of Mars: It is not entirely clear how Horus managed to turn such a significant percentage of the armies under his command against the Emperor, but he was known to be a very skilled and persuasive leader who commanded immense personal loyalty amongst his subordinates. But even before the opening stages of his planned insurrection occurred, he knew he would have to secure the support of the Adeptus Mechanicus and their superior technology and weapons if he was to defeat the Emperor and conquer the galaxy. Horus won over the loyalty of many of the Mechanicus' Tech-Adepts after promising them the lost secrets of ancient Standard Template Construct (STC) technology that had been recovered from the worlds of the recently subjugated Auretian Technocracy by the Sons of Horus Legion.The Heresy also struck at the technological and industrial heart of the Imperium on the Forge World of Mars, the sacred homeworld of the Mechanicum. The climate on Mars was full of discontent during this tumultuous time. There were tense relations between the various Techno-Magi with sporadic outbreaks of espionage and violence being committed against the various forges that represented the primary sociopolitical units of Mars. There were even unconfirmed suspicions that the Titan Legions had already secretly chosen sides in case of a potential conflict. Regulus, the Adeptus Mechanicus' representative to the Warmaster Horus who had already thrown in his lot with the Warmaster, was sent to Mars to secure the tentative support of the Fabricator-General of Mars, Kelbor-Hal. Regulus convinced the Fabricator-General of Horus' resolve to support increased autonomy for the Mechanicum under his rule rather than maintaining the more autocratic mandates of the Emperor that prevented the Mechanicum from doing exactly as it pleased. As a show of his appreciation for the Fabricator-General's support, Horus provided information to Kelbor-Hal that allowed the Mechanicum to open a repository of forbidden knowledge known as the Vaults of Moravec, which had been sealed for a thousand years. The Emperor Himself had decreed that the vaults never be opened, for they contained innumerable artefacts of technology that had been fashioned or corrupted by the malign power of Chaos. But the deal was struck,and the Fabricator-General accepted Horus' proposal and joined forces with the Warmaster, assisting the Traitors with all of the technology of Mankind at his disposal.When this repository was reopened, there was all manner of forbidden arcane knowledge and weaponry that had obviously been tainted by the corrupting influence of Chaos stored within. Soon the corruption spread throughout the forges and temples across the Red Planet as scrap code -- Chaos-contaminated digital source code that was infected with an arcane computer virus -- infested the logi-stacks and Cogitator (computer) archives of the Adeptus Mechanicus, causing literal Chaos to emerge in any Cogitator system that was networked to one of its infected counterparts. The Fabricator-General and his Dark Mechanicum allies used this disruption to marshal the strength of their forces, intent on bringing the rule of Mars firmly under their control. Many Mechanicus forces that remained loyal to the Emperor as the embodiment of the Omnissiah were forced off-line or destroyed outright by the traitorous Fabriactor-General's ploy. In later years, the night the Chaos code was released would become known in Mechanicum legends as the Death of Innocence.Open warfare erupted on the Red Planet in the wake of the Death of Innocence as Martian forces, both civilian and military, fought one another in a deadly civil war that mirrored the larger conflict consuming the Imperium. This internecine conflict became known as the Schism of Mars. Across the galaxy, open rebellion erupted as Space Marine Legion fought Space Marine Legion and Titans battled Titans. The members of what became known as the Dark Mechanicus supported Horus throughout the Horus Heresy and used dark and forbidden knowledge revealed by the Ruinous Powers to help destroy the Loyalist forces.