The Abyss is the birthplace of demons. It is a chaotic universe comprised of uncountable layers of infinite variety, all connected haphazardly. It is a violent, malevolent place where the strong survive on the backs of the weak; the weak conspire to overthrow the strong; and--much unlike the lawful Baator--alliances last only while convenient.
The landscape itself tortures the mind and body of all who dare to pass.
Demon Lords and Princes
Each layer is ruled by a demon lord--a being who has proven him- or herself to be the most powerful upon it. In certain cases, an individual manages to gain dominion over more than one layer. These cases are rare, and those that accomplish the feat are generally considered deities (although the term Demon Prince is more commonly used).
Some notable princes include:
Gateway to Pandemonium
In time immemorial, the realm of Graz'zt came to believe it too destructive to be contained. He and his cohort--in an act still thought by many to be beyond their combined power--managed to sever its connection to the Abyss entirely. In an instant, Pandemonium became a plane unto itself.was once a layer of the Abyss. However, the demon prince
Somewhere among the remaining layers is rumored to be a portal to Pandemonium, but its location is a heavily-guarded secret (if not simply a hoax).