The Battle of Cthonis was an engagement between the Imperium of Man and a large force of Orks in 999.M41, on the Forge World of Cthonis. The Orks -Having been instigated by Abaddon the Despoiler to invade- were planning to seize control of the planet's valuable Warlord-class Titans, and use them to conquer other nearby Imperial worlds. Abaddon had secretly planned to betray the Orks at the last moment when they had seized the Titans, and claim the war machines for himself, avoiding direct assaults onto the Forge World as he did not want to postpone his imminent Black Crusade, which required all available troops of his.