The 13th Black Crusade of Abaddon the Despoiler that began in 999.M41 resulted in the largest clash between Imperial and Chaos forces seen in the Milky Way Galaxy since the Horus Heresy ten thousand Terran years before. Abaddon raised the greatest army in service to the Chaos Gods since the time of Horus, and intended to bring an end to the Long War by driving on Terra, slaying the Emperor of Mankind upon His Golden Throne and at last completing the task the Traitor Legions had begun millennia before.