Ezekyle Abaddon, the First Captain of the Sons of Horus, played a significant role in the Horus Heresy. Abaddon was crucial in making the decision among the other advisers of the Mournival to deliver Horus into the hands of the Chaos Sorcerers of the Davinite Temple of the Serpent Lodge, a Chaos Cult, which resulted in Horus' ultimate corruption during a sojourn of his spirit in the Warp caused by a ritual conducted by the Word Bearers First Chaplain Erebus. Afterwards, Abaddon become Horus' strongest supporter in his rebellion against the Emperor and helped lead the forces of the Sons of Horus in every action the XVI Legion fought during the civil war, up to and including a prominent role in the Siege of Terra. When Horus was slain by the Emperor, it was Abaddon who led his shattered Legion into the Eye of Terror, before abandoning them in despair for a time.