|This article is about the Thousand Sons Space Marine; for the Night Lords Space Marine, see Karlsen (Night Lords).|
Once a Captain of the Thousand Sons, Karlsen became a Champion of Tzeentch and a veteran of the Long War, having fought against the Imperium since the Horus Heresy. A Sorcerer, Karlsen took part in nearly all of his Legion's significant history, including the fall of Prospero, the Battle of Terra and countless other combat actions. His lifespan unnaturally extended by his Chaotic patron, Karlsen went completely insane on more than one occasion due to the burden of his experiences, though he performed the ritual of the Dark Communion on his mind whenever he could to safely store his memories. Karlsen has noticeable mutations: one of his hands is fused to his bolter and he operates the weapon by mental control, whilst the fingers of his other hand have lengthened to become almost tentacle-like.