The Abyss

The Infinite Layers of the Abyss was the birthplace of the demons, a chaotic evil universe unto itself with uncountable layers of infinite variety connected haphazardly. The nature of the plane has remained fairly constant: a violent, malevolent place where the strong survived on the backs of the weak, the weak conspired to overthrow the strong, alliances only lasted while convenient, and the landscape itself tortured the mind and body of all who dared to pass.

The Abyss includes the planes of Hell and The River Styx.