This is an excerpt from the Planar Handbook
The various planes of existence in the D&D cosmology follow the Great Wheel model. The Great Wheel is a straightforward concept. The world of “reality” that most people think of as the only plane of existence is called the Material Plane. The Material Plane is coexistent with the dreamlike Ethereal Plane, which means the two planes occupy the same space, but it is coterminous with the Astral Plane, which means that the Material and the Astral share a common border. Fornhabitants of the Material Plane, the Astral Plane is the gateway to the divine Outer Planes and the elemental Inner Planes. When you throw in the many
other extradimensional spaces known as demiplanes, the Great Wheel model describes the multiverse in all its infi nity.
THE MATERIAL PLANE
The Material Plane is the world that hosts most D&D campaigns. It is the most Earthlike of all planes and operates under the same set of natural laws that our own real world does. Even though the Material Plane is a comfortable place for PCs, it is
a strange and dangerous environment for many creatures that are native to other planes but fi nd themselves on the Material Plane at least temporarily (perhaps as the result of a summon monster spell or similar magic).
THE TRANSITIVE PLANES
Transitive planes are used to get from one place to another; however, many natives of the transitive planes rarely fi nd it necessary to venture from their strange realms. There are three so-called transitive planes: the Astral Plane, the Ethereal Plane, and the Plane of Shadow. The Astral Plane is a conduit to all other planes, while the Ethereal Plane and the Plane of Shadow both serve as means of transportation within the Material Plane they’re connected to. These planes have the strongest regular interaction with the Material Plane and are often accessed by using various spells.
Travelers within the most interconnected transitive plane, the Astral Plane, may fi nd it benefi cial to visit the city of Tu’narath (see Planar Metropolises)—provided they
take the proper precautions.
THE INNER PLANES
The Inner Planes are elemental manifestations, pure substances from which the rest of the multiverse is constructed. Each Inner Plane is made up predominantly of a single type of energy or element that overwhelms all others. The natives of a particular Inner Plane are made of the same energy or element as the plane itself. The six Inner Planes are the Elemental Plane of Air, the Elemental Plane of Earth, the Elemental Plane of Fire, the Elemental Plane of Water, the Negative Energy Plane, and the Positive Energy Plane.
Travelers who stray onto the very dangerous Elemental Plane of Fire will probably be best served if they visit the
City of Brass (see Planar Metropolises), assuming they have leave to do so.
THE OUTER PLANES
Deities make their homes on the Outer Planes, as do demons, devils, and angels. Each of the seventeen Outer Planes has an alignment, representing a particular moral or ethical outlook, and the natives of each plane tend to behave in agreement with that plane’s alignment. The Outer Planes are also the fi nal resting place of souls from the Material Plane, whether that fi nal rest takes the form of calm introspection or eternal damnation.
One of the most legendary cities of all lies on the Outer Planes: the city of Sigil. Planar travelers of all stripes can find profi t there (see Planar Metropolises).
Demiplanes are extradimensional spaces that function like planes but have measurable size and limited access. Other kinds of planes are theoretically infi nite in size, but a demiplane might be only a few hundred feet across. Some demiplanes are easily reached through portals, while others may be more diffi cult to enter. Generally, access to a demiplane is limited to a particular location (such as a fi xed gateway) or a particular situation (such as a time of year or a weather condition). Some demiplanes
are created by powerful magic, some naturally evolve, and some appear according to the will of the deities. Demiplanes rarely show up in diagrams purporting to show the “geography of the planes” because the location and even the existence of these extradimensional spaces is constantly changing.
A trading city located on a demiplane named Union, formed eighty years ago, has become known for the extreme volume of trade moving through its streets, as well as for the exceptional abilities of many of its citizens.