The planes of the Dungeons & Dragons roleplaying game constitute the multiverse in which the game takes place. Each plane is a universe with its own rules with regard to gravity, geography, magic and morality. There have been various official cosmologies over the course of the different editions of the game; these cosmologies describe the structure of the standard Dungeons & Dragons multiverse. The concept of the Inner, Ethereal, Prime Material, Astral, and Outer Planes was introduced in the earliest versions of Dungeons & Dragons; at the time there were only four Inner Planes and no set number of Outer Planes. This later evolved into what became known as the Great Wheel cosmology. The 4th Edition of the game shifted to the World Axis cosmology. The 5th Edition brought back a new version of the Great Wheel cosmology which includes aspects of World Axis model. In addition, some Dungeons & Dragons settings have cosmologies that are very different from the "standard" ones discussed here. For example, the Eberron setting has only thirteen planes, all of which are unique to Eberron. Publication history The cosmology of the planes was presented for the first time, as part of the Great Wheel of Planes, in Volume 1, Number 8 of The Dragon, released July 1977. In the article "Planes: The Concepts of Spatial, Temporal and Physical Relationships in D&D", Gary Gygax mentions that there are 16 Outer Planes. The "Basic edition" of D&D had a separate, though similar, cosmology from that of its contemporary AD&D game, which is more open and less regulated than that of its counterpart. The planes were further "refined in the Players Handbook (1978) and Deities & Demigods (1980)". The appendix of the Player's Handbook included an abstract diagram of the planes, and mentioned the same 16 Outer Planes. Shannon Appelcline, the author of Designers & Dragons, highlighted that throughout the early 1980s Dragon magazine would continue to detail "some of the planes in more depth", however, "there was no overarching plan for the planes of D&D other than a few increasingly old drawings". The D&D multiverse was expanded with the D&D Immortals Rules (1986) set. The Astral Plane permeates and connects the rest of the Multiverse. Plane sizes can vary from the Attoplane (one-third of an inch across), through the Standard Plane (.085 light-years across), to the Terraplane (851 billion light years across), with stars and planets varying