Orkamungus was the Ork Warboss in charge of the Ork tribes who launched an invasion of the planet Tartarus, an Imperial Civilised World, to serve as a cover for the attempt of the Alpha Legion to recover a potent Chaotic artefact known as the Maledictum before the world was consumed by an oncoming Warp Storm.
Orkamungus dominated several large Ork clans, and unleashed his WAAAAGH! upon the planet of Tartarus, quickly isolating the major Imperial cities and overrunning the defenders with an unstoppable tide of Ork Boyz. Orkamungus led the assault in person on a vitally important spaceport that the 37th Tartarus Planetary Defense Force Regiment was using in an attempt to evacuate civilians from the doomed world. The tidings of battle soon turned, however, as the Blood Ravens Space Marines arrived on the battlefield by Drop Pod and held back the green tide of Orks.
Unbeknownst to everyone, Orkamungus had been bribed and armed by Bale and Sindri Myr, two Chaos Lords of the Alpha Legion, to mount the invasion that would distract the Imperials from their search for the Maledictum. His strategy of mostly attacking cities was both satisfying to the Orks' lust for war, and pinned down the Imperial Guard and Space Marines in defensive positions, allowing the servants of the Ruinous Powers to remain hidden. Orkamungus ultimately attracted the attention of the Blood Ravens' 3rd Company, and was killed when the Blood Ravens fell upon his base in force.
Orkamungus wielded a Kustom Power Klaw in melee combat and a large Kustom Shoota that was powerful enough to be able to pick off an entire enemy squad from afar. Orkamungus wore a cybernetic Ork combat exoskeleton which greatly increased his strength and durability.
- Dawn of War (PC Game)