Zahariel - The Fall: Fifty Terran years later, following the great success in the recruitment, training, and equipping of new Astartes for the Dark Angels, Luther and his lieutenants, including Zahariel, who had himself begun to feel something of Luther's betrayal by their primarch, were faced with a widespread rebellion on Caliban. Following Librarian Zahariel's investigations, it was revealed that Caliban was plagued by a resurgence of the Great Beasts that had once run amok across the Dark Angels' homeworld.This dire threat was further compounded by the insurgency raised against them which included former knights of The Order who felt that the Lion had betrayed them. At the centre of this conspiracy was a mysterious cabal of Terran-born bureaucrats who were actually Chaos Cultists and sorcerers that were somehow linked to the reemergence of the Warp-spawned beasts and hordes of undead who began to assault Calibanite settlements.Learning of the Warmaster Horus' rebellion against the Emperor and the start of the Horus Heresy, Luther decided that in the best of interests of Caliban, he was compelled to declare their world's independence in opposition to both Terra and their primarch alike. Zahariel vehemently disagreed with this course of action initially, but the more he learned of Caliban's dark past and its connection to the Warp, the more he agreed with Luther. Finally, after defeating the cabal of Chaos Sorcerers and their walking dead with his own psychic abilities, Zahariel knew there would be no turning back for Caliban due to the Edicts of Nikea and he decided to join Luther in secession. Zahariel went on to become one of the first of the so-called Fallen Angels.Later on Caliban, Zahariel was running through a collapsing tunnel before he was buried beneath its falling mass, left for dead by the Lord Cypher during an expedition against more of the Chaos forces that had afflicted Caliban. While trapped beneath the stone, his mind drifted to the past about an old cave with a wizard before awakening again. Moving through an opening, he came upon the undead who he dispatched with his psychic powers, causing them to withdraw.He quickly looked for the worms that they battled when they fought the Ouroboros and found a psychic void that was growing that he determined was an emanation of the Ouroboros itself, a sentient Warp device deeply hated by the Watchers in the Dark, who feared its Warp-tainted power. With the sudden realisation that he was inside of the worm and cut off from his psychic power, Zahariel blacked out. Later when he finally returned from beneath Caliban, his personality had been changed by the experience and exposure to the Ouroboros, becoming darker and more resentful. Zahariel now insisted that the Ouroboros was actually the embodiment of Caliban itself and not an enemy of the Dark Angels.This belief brought Zahariel into conflict with the Lord Cypher who wished to maintain his influence over Luther. Later, when Zahariel learned of the death of his cousin Nemiel at the hands of the Lion, Zahariel became even more embittered against the Dark Angels primarch and this contributed to him leading a purge against a group of recently arrived Legion Loyalists on Caliban led by Belath.Through the power of the Ouroboros, Zahariel saw Cypher as a green man, a man born of a tree and thus embued with the essence of Caliban's world-straddling forest. The two sides disputed the nature of the planet. He then confronted Cypher, and was surprised by the man's true identity before killing him. Following these events, Zahariel was elevated by Luther as the new Lord Cypher.