In practice, worlds with physical connections tend to have adjacent numbers, and realms with a higher number are more distant from the first layer and thus harder to reach. The numbering system used was developed by the Fraternity of Order, a guild of planar explorers who simply numbered the layers in the order they were discovered. Controlling at least one level of the Abyss usually qualifies a demon to claim the rank of demon lord. Each has its own unique and terrible terrain. The Abyss is unique in that it is divided into an uncountable number of independent planes.
It is chaotic evil in alignment, and best known as the home of demons, including the numerous varieties of tanar'ri. The Abyss, also known as The Infinite Layers of the Abyss, or Demonholme, is one of the planes of existence in Dungeons & Dragons.
