Plane (Dungeons & Dragons)

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.

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 a more open planar system that is 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 multiverse of the Basic D&D game was expanded with the D&D Immortals Rules (1986) set. The Astral Plane runs through and links the rest of the Multiverse. Plane can range in size from the tiniest Attoplane (1/3 inch long), to the Standard Plane (.085 light-years long), up to the Terraplane (851 billion light years long), with stars and planets scaled to match the size of the plane.

Both Appelcline and Curtis D. Carbonell, in his book the Dread Trident: Tabletop Role-Playing Games and the Modern Fantastic, highlighted that information on the planes and the shared cosmology was codified in the Manual of the Planes (1987) and Tales of the Outer Planes (1988). Carbonell wrote that project leader and designer Jeff Grubb detailed "the schematization of the planes' requisite five area: the Prime Material, the Ethereal, the Astral, the Inner, and the Outer planes. This basic structure is still used in 5e, with some changes that provide minor rearrangements and clarifications [...]. Grubb's approach demonstrated a need to codify, while still remaining flexible, that has remained as a primary aim of the latest edition".

Carbonell also highlighted that the 1989 Spelljammer campaign setting added cosmology that "allowed travel between the different settings" such as Dragonlance, Greyhawk, and the Forgotten Realms. However, campaign settings such as Dark Sun and Ravenloft were inaccessible in this cosmology. Then in 1993, TSR wanted to do a series of books about the Outer Planes which Zeb Cook said led to the creation of the Planescape campaign setting released in 1994. This campaign setting provided a framework to create adventures across the planes with the city of Sigil acting as a hometown and starting point for players. Carbonell called this setting "the most complex example of the multiverse created during the varieties of 2e's AD&D settings" and wrote: "A more nuanced and sophisticated attempt at harmonization, Planescape provided an alternate way to travel between the planes than Spelljammer's science-fantasy-oriented approach". The 3rd edition Manual of the Planes (2001) detailed both the inner and outer planes. Kevin Kulp, for DMs Guild, wrote that "the authors used an approach that said 'here's how it's been done in the past, and here are other ways you can do it,' which allowed the book to avoid setting planar mechanics in stone. Instead it gave DMs a modular approach by presenting Options, a flexible strategy that pleased both 1e and Planescape fans. Vast amounts of new ideas and new locations were presented, dovetailing nicely with canon from earlier editions".

The 4th edition shifted the locations of the various planes to fit the new World Axis cosmology and added the Parallel Planes of the Feywild and the Shadowfell to the game; many of the changes were detailed in that edition's Manual of the Planes (2008). However, the 5th edition Player's Handbook (2014) and Dungeon Master's Guide (2014) shifted most of the cosmology of the planes back to the Great Wheel model with some aspects of the World Axis model retained in the descriptions of the inner planes.