Ahriman - Horus Heresy: Before the Horus Heresy began, Ahriman had risen to the powerful position of Chief Librarian of the Thousand Sons Legion, the captain of its 1st Fellowship and the leader of the Sekhmet or Scarab Occult who served as the elite Veterans of the Legion and deployed in Terminator Armour.Ahriman was also one of the leaders of the Thousand Sons' most powerful sorcerous cult, the Corvidae, who were skilled in the psychic discipline of precognition, which was the ability to determine the likely probabilities of future events. They served as the Legion's seers, warning their battle-brothers of dangers before they materialised. The Corvidae Cult also helped guide the Thousand Sons Legion along the lines of Fate during times of conflict and in pursuit of their overall psychic and material growth as a Legion, as well as serving as the Legion's primary strategic planners. Ahriman had come to share his primarch's obsession with the pursuit and preservation of arcane knowledge and the unraveling of the mysteries of the Warp.Though the Thousand Sons had been ordered by the Emperor to cease and desist all psychic activities and dabbling in the occult, Amon, the captain of the 9th Fellowship and Magnus' father figure and former mentor, 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 Prospero's capital city of Tizca. Amon and Ankhu Anen, Guardian of the Great Library of Prospero and member of the Corvidae Cult, shared Ahriman's knowledge that something was very wrong, but even their combined power was unable to pierce the veils of the future to see what so concerned their primarch.In truth, 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 Earth. Though Magnus did not exactly know the means by 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 the Feral World 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 Human-ruled galaxy asunder. The works that Magnus had Amon researching since the end of the Council of Nikaea held the key to Horus Lupercal's salvation. With the help of his fellowship captains, Magnus intended to telepathically project himself into the Immaterium and attempt to shield his brother from his enemies.When Horus fell, mortally wounded by the poisoned xenos blade known as the Kinebrach Anathame on the moon of Davin, First Chaplain Erebus of the Word Bearers Legion, who had been seconded to the Luna Wolves Legion as an advisor, saw his chance to further his own designs for the Chaos Gods. He persuaded the Luna Wolves' Warrior Lodge to allow a group of Abhuman 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 creeds of the Imperial Truth.During the dark rituals that followed within the Chaos temple, Horus' soul 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 worshipped as a god and his angels by the masses of Humanity. 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 future actions.Magnus had also travelled into the Warp via the use of ritualistic sorcery to try and stop Horus from turning to Chaos. Magnus explained that the Warmaster's vision was only one of many possible futures, but one that Horus alone could prevent. Horus, already jealous toward any perceived threat to his own greatness and resentful of what he perceived as his abandonment by his father the Emperor, proved all too receptive to the Ruinous Powers' false vision.During his sojourn in 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 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 to achieve this knowledge -- whatever the cost might be.