Great Beast

The Great Beast is the name given to the theoretical god of Chaos Undivided.

By its very definition, Chaos claims no allegiance to anything but itself. The Gods and followers of the Chaos Gods are fractious and warlike in the extreme, and view each other with suspicion and disgust. Hordes of Chaos Warriors are drawn together not out of camaraderie, but out of a mutual desire to murder, burn, and slaughter in the name of their Gods. A follower is just as likely to be killed and offered as a sacrifice to his own God as he is to die in battle with the forces of the Old World or against his foe.

Some insane scholars believe that the four powers are simply aspects of some other, larger God called the Great Beast. At times, this entity sets aside its mad internal struggle to make it possible for the fragmented armies to gather together under one banner, such as the Chaos Incursions. These moments cause the Old World to tremble and quake in fear and loathing. The followers of Chaos typically come together under the banner of a particularly powerful and charismatic leader. Driven by dreams of mayhem, loot, and glory in battle, the forces of the various factions of Chaos set aside their differences for a short time to fight side by side. The people of the Old World know that it’s just a matter of time before another leader inspires the hordes of Chaos to come together yet again. Whether there exists a Great Beast or not is subject to much debate, but certainly the effects of Archaon’s Storm of Chaos are undeniable.

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption pg. 199