Magnus the Red - Magnus' Folly: Following the great Imperial victory during the Ullanor Crusade against the Orks, the Emperor gave overall command of the Great Crusade to Horus of the Luna Wolves Legion, awarding him the title of Warmaster over all Imperial armies, including the Legions of his brother Primarchs. The Emperor then departed the Crusade and returned to Terra to pursue his secret project to expand the Eldar Webway for human use beneath the Imperial Palace. Magnus, meditating on Prospero, psychically foresaw Horus being corrupted by the malign influence of the Ruinous Powers and the future events of the Horus Heresy: the betrayal of the Emperor by half the Space Marine Legions, and the sundering of the Imperium by a tumultuous and costly civil war. The only fate the vision did not reveal to Magnus was his own. Burdened with this volatile information by this precognitive vision, Magnus decided upon a course that would seal his fate. First, Magnus attempted to psychically contact his brother Horus, but to his dismay, found out that he was too late, and that the Warmaster had already been nigh mortally wounded by a stab from the Kinebrach Anathame.Despairing, Magnus then decided to utilise the power of his Legion's greatest sorcerers to convey the news of the impending civil war to the Emperor Himself on Terra via sorcery, rather than using the far slower, but legal means of astrotelepathy. Using an astral projection spell, the spirit of Magnus the Red hurtled towards Terra through the Warp. While in the Immaterium, Magnus came across a Webway corridor that led to Terra but found the barrier impenetrable. But then an anonymous entity within the Warp whispered sibilantly to him, offering to provide the Primarch with additional power in order to breach the Webway. Magnus seized upon the entity's offer, breaching the barrier and bursting into the Emperor's throne room. This act penetrated the powerful psychic wards the Emperor had raised around the Imperial Palace and allowed Warp entities to penetrate the human extension of the Webway and launch an assault against Terra itself, killing thousands of the Mechanicus Adepts who had been labouring with the Emperor on his great work. With this breach, the Emperor's work was undone. Horrified, the Primarch's spirit returned to his corporeal body on Prospero. There, he received a vision from Tzeentch, the mysterious entity that had enabled him to breach the Webway. The Architect of Fate informed Magnus that it was his destiny to serve the will of the Ruinous Powers.The Emperor was furious at Magnus' willful violation of the proscriptions against the use of sorcery set by the Council of Nikaea, especially because Magnus had used the Webway to reach Terra in time, and his actions had damaged the secret Webway Project, a centuries-long attempt to use this Eldar construct to render dangerous Warp travel obsolete and physically connect all the worlds of the Imperium of Man together using human versions of the Eldar's Webway portals. The Emperor saw Magnus as the traitor to the Imperium's ideals, not his beloved son Horus, whom he did not believe was capable of betraying him. Leman Russ, Primarch of the Space Wolves Legion, who had always been averse to sorcery and had a general antipathy to Magnus as a result, was ordered to bring Magnus swiftly to Terra to account for his actions before the Emperor. During his voyage to Prospero, Leman Russ was instead ordered by an already corrupted Horus to destroy Magnus' Thousand Sons Legion rather than simply bring them to account. Horus, as the Imperial Warmaster, carried the authority of the Emperor Himself, and was therefore able to fool Russ into believing this was the Emperor's will as if the Emperor had thought about his decision and changed his mind. Accompanying the Space Wolves were a full contingent of Adeptus Custodes, millions of Imperial Army troops, and the elite Imperial anti-psyker (Pariah Gene-bearing) witch hunters known as the Sisters of Silence.