A Blood Cult is the name given to those Chaos Cults that specifically worship the Blood God Khorne. While warbands of Heretic Astartes practice their worship of the Lord of Skulls openly, mortal cultists gather in backrooms and secret slaughter tunnels beneath crowded streets, plotting murder and bloodshed in Khorne's name. Given the terrible socioeconomic nature of many Imperial worlds, however, locals often barely notice increases in violent crimes, missing persons, and gory dismemberments, allowing Blood Cults of Khorne to ﬂourish below the rot of society.
The members of these cults have many different reasons for joining together. Some have seen a friend die in a bar fight. Others have lost their families as collateral damage in Adeptus Arbites raids. There are even those who fight for sport because they enjoy the feeling of fists shattering jawbones. All these reasons and more can set a man on the path toward Khorne. Vengeance and combat are intoxicating to those predisposed to revel in them. This feeling drives individuals to want more, to be strong enough to topple greater foes, and to seek the power necessary to do so. No matter the reason that brings them together, when these individuals find each other, they are united by a common desire. They wish to kill, offering blood and skulls in exchange for power and retribution, and Khorne has much to offer them in the bargain.
- Black Crusade: The Tome of Blood (RPG), pg. 17