The Invocators are a warband of Chaos Space Marines. They were once a Loyalist Chapter of Space Marines of unknown origin and Founding, known as the Clerics of Steel. They were corrupted after entering the Eye of Terror in 321.M37 as part of the Imperial Abyssal Crusade. It is unknown what they endured during their sojourn into the Eye, but by the time they made their way back into realspace, they had become the warband of Chaos Space Marines known as the Invocators.