Abaddon, also known as Abaddon the Despoiler, once named Ezekyle Abaddon, is the Warmaster of Chaos, a Chaos Lord and the greatest Champion of Chaos Undivided in the galaxy. He is the commander of the Black Legion of Chaos Space Marines and is rumoured to be the clone-progeny of the Warmaster Horus, the greatest Traitor in Imperial history, and at one time his most favoured son amongst the Space Marines of the Sons of Horus Legion. He is now infamous for leading Black Crusades, the terrible military campaigns during which the normally fractious Forces of Chaos unite under his leadership and launch a massive attack against the Imperium from within the Eye of Terror. The most recent of these attacks, the 13th Black Crusade in 999.M41, led to the partial capture of the vital Imperial Fortress World of Cadia and an expansion of Chaos-controlled space into Imperial territory for the first time since the Horus Heresy.