Abyss

The Abyss is an infinite plane of chaos and evil. Unlike the Nine Hells' strict hierarchy, the Abyss is chaotic and unorganized.

The Abyss is one of the Outer Planes, separated from the mortal planes by the Divine Gate. The mad deity Tharizdun, the Chained Oblivion, dreams its infinite depths and demon hordes into being, and since Tharizdun's defeat at the hands of Pelor in the Calamity the god has been shackled in the deepest pits of the Abyss.