These mysterious warriors first appeared during the insurrection on the world of Magma Codelian. The Loyalist Guardsmen of the Astra Militarum's 334th Iridian Regiment had pushed their way into the rebellious planetary governor's palace after a sustained bombardment.
The regiment's Primaris Psykers realised too late that the architecture of the governor's keep was actually a gigantic summoning circle. Amongst the choking fumes, the insurrectionists conjured reinforcements; not Daemons, but Chaos Space Marines with strange, oil-like blood oozing from the joints in their armour.
Though the new arrivals were massively outnumbered, the power armoured warriors exhibited an incredibly high pain threshold, fighting on through mortal wounds to eventually repel the Iridians' attack and secure the planet for the insurrectionists.
- Against the Dark Angels (891.M39) - The Cleaved appeared out of a newly materialised space hulk. Battling the Dark Angels who responded to the Heretic Astartes' emergence into realspace, the Loyalist Astartes emerged victorious when their Assault Squads, emerging behind a trio of Dreadnoughts, got close enough to set off cyclonic charges in the space hulk's engine room.
- Cholercaust Blood Crusade (Unknown Date.M41) - The Cleaved joined the massive Khornate force known as the Cholercaust which followed the path of the Keeler Comet and brought war and ruin to the worlds in its path. The Cholercaust Blood Crusade was finally stopped by a small coalition of Imperial forces on the Cemetery World of Certus-Minor. The Cleaved and other Traitor Marines took to the field under the command of Lord Umbragg of the World Eaters and participated in the final attack on Obsequa City. The Cholercauset suffered a total defeat and all in its ranks were slain, including the Thunder Barons. It is unknown if the entire warband took part in the Blood Crusade, and whether or not Cleaved remnants still exist elsewhere.
- Invasion of Medusa (Unknown Date.M42) - Alongside warbands of The Cleaved, The Purge and several other Nurglite Renegade forces, Typhus led the Death Guard's 1st Plague Company in a shocking raid against the Iron Hands' Chapter Planet, Medusa. The Iron Hands' clan companies drive off their attackers, but not before terrible damage is done, leaving regions of the planet as cursed quarantine zones.
The Cleaved wear pale, flesh-coloured power armour that seems to have a strange, oil-like substance constantly oozing from the joints of the armour like black blood. What remains of the Chaos Space Marines within their sealed armour, or how they have been mutated to release such a discharge, none can say.
The Cleaved warband's badge is a pair of ebon-coloured, crossed battle-axes centered on a field of pale, dirty white. They also wear the usual heretical Chaos icons and fetishes dedicated to the Plague God. This usually takes the form of a Mark of Nurgle.
- Codex: Chaos Space Marines (4th Edition), pg. 68
- Codex: Chaos Space Marines (6th Edition), pg. 16
- Codex: Dark Angels (6th Edition), pp. 36-38
- Codex Heretic Astartes - Chaos Space Marines (8th Edition) (Revised Codex), pg. 51
- Codex Heretic Astartes - Chaos Space Marines (8th Edition), pg. 51, 110
- Codex Heretic Astartes - Death Guard (8th Edition), pg. 22, "The Gorgon's Lair"
- White Dwarf 333 (UK), "Battle Report - The Karis Cephalon Incursion," pp. 49, 51
- The Legion of the Damned (Novel) by Rob Sanders