High Quality Content by WIKIPEDIA articles! In the Dungeons & Dragons fantasy role-playing game, the Abyss, or more fully, the Infinite Layers of the Abyss, is a chaotic evil-aligned plane of existence. It is one of a number of alignment-based Outer Planes that form part of the standard Dungeons & Dragons (D&D) cosmology, used in the Planescape and Greyhawk campaign settings. The Abyss is also the name of one of the faith-based outer planes that form part of the Forgotten Realms cosmology. While the published 3rd-Edition source books indicate that the Abyss of the standard D&D cosmology is not the same plane as the Abyss of the Forgotten Realms cosmology, they are for all practical purposes identical.