Amon - Horus Heresy: Though they had been ordered by the Emperor to cease and desist all psychic activities and dabbling in the occult, Amon willingly went along with his primarch's decision to continue with their studies of the Warp. Magnus was keeping a monstrous secret from his captains while he worked feverishly and alone in his private library and the vaults beneath Tizca.Amon and Ankhu Anen, Guardian of the Great Library of Prospero and member of the Corvidae Cult, had shared Ahriman's knowledge that something was wrong, but even their combined power was unable to pierce the veils of the future to see what so concerned their primarch. Magnus had foreseen a terrifying vision of the Warmaster Horus falling from grace and dragging the burgeoning Imperium of Man into a war more terrible than any of them could imagine -- an Age of Darkness that had been prophesied tens of thousands of standard years before by the ancient Aegyptos of Old Terra.Though he did not exactly know the means in which Horus would fall, all he could perceive from his vision is that something primordial and corrupt would take root in his soul. Magnus had foreseen that the Luna Wolves Legion would soon be making war on a moon of Davin, and the fates were conspiring to fell Horus with a weapon of dreadful sentience.In his weakened and blinded state, the enemies of all life would make their move to ensnare his warrior heart. Without the intervention of the Thousand Sons, they would succeed and split the galaxy asunder. The works that Magnus had Amon researching since the Council of Nikaea held the key to Horus Lupercal's salvation. With the help of his fellowship captains, Magnus would project himself across the Warp and attempt to shield his brother from his enemies.During the battle against Chaos-spawned undead on Davin's moon, whose Planetary Governor, Eugen Temba, had been corrupted by the forces of the Chaos God Nurgle, Horus was poisoned by a xenos blade dedicated to Nurgle known as the Kinebrach Anathame that had been stolen from the human civilisation of the Interex by First Chaplain Erebus of the Word Bearers.This occurred after Horus and the Luna Wolves of the 63rd Expeditionary Fleet had made a disastrous first contact with that Human civilisation. Erebus then gifted the weapon to the Chaos-corrupted form of the Imperial Army commander Eugen Temba who the Warmaster had left behind to govern Davin sixty standard years before.Once Horus had been mortally wounded by the arcane weapon, Erebus saw his chance to further the designs of Chaos, persuading the Luna Wolves' Warrior Lodge to allow a group of Davinite shamans -- Chaos Cultists all -- located on the surface of Davin at the Temple of the Serpent Lodge to heal him. The Luna Wolves, besides themselves with grief and the fear that their beloved primarch would die, agreed to the suggestion, despite its direct violation of the atheistic creeds of the Imperial Truth.During the dark rituals that followed within the temple, Horus' spirit was transferred from his body into the Immaterium. There, he bore witness to a nightmare vision of the future. He saw the Imperium of Man as a repressive, violent theocracy, where the Emperor and several of His primarchs (but not Horus) were worshiped as gods by the masses. While this vision of the Imperial future granted by the Chaos Gods was a true one, it was ironically an outcome largely created by the Warmaster's own actions.Magnus had also travelled into the Warp via sorcery to try and stop Horus from turning to Chaos. Magnus explained to Horus within the Immaterium that the Warmaster's vision was only one of many possible futures, but one that Horus alone could prevent. Horus, already jealous and resentful of the Emperor for leaving the Great Crusade behind to work on the Imperial Webway project, and fearful that when the Great Crusade ended he would have no further chance to win glory and amdiration, proved all too receptive to the Ruinous Powers' manipulation.During his sojourn across the Warp, Magnus realised the treachery ran deeper than he had first thought. It seemed the powers that sought to ensnare Horus had already claimed others of the Imperium who were in thrall to Chaos -- Lorgar and his Word Bearers.Now that events had been set in motion, Magnus ordered Amon, Ahriman and the rest of the Corvidae Cult to unravel the strands of the future. The Thousand Sons needed to know more of what was to come. He ordered them to do whatever it took -- whatever the cost might be.