The Thunder Barons are a Renegade Chapter of Chaos Space Marines of unknown origin. Formerly a Loyalist Chapter of Astartes, they eventually spat on their oaths to the Emperor of Mankind and instead swore their allegiance to the Chaos Gods, and to the Blood God Khorne in particular. Since their fall to Chaos, the Thunder Barons have become obsessed with looking for amulets and artefacts of arcane power that will enhance their abilities in combat -- and provide more victims for the Blood God's pleasure.