Types of Worlds

For purposes of this discussion, a world is any place in the multiverse with its own form of reality separate from the rest of the multiverse. A world can be as large as a universe or as small as a single room. Worlds in the current AD&D game fall into one of three different types:

Plane: A plane is an infinitely large space. A plane has no clear form or dimensions, though there are border areas where it meets other planes. As explained in Chapter 15 of the Dungeon Master Guide, there are three types of planes and two planes that defy categorization.

Inner Planes are places filled with the fundamental components of the multiverse. There are 18 inner planes. They are subdivided into elemental (basic matter), para-elemental (compound forms of matter), energy (positive and negative), and quasi-elemental (where planes of matter and energy meet). If there are any undiscovered inner planes, they likely exist between known planes.

Outer Planes are places where the powers (deities) reside. A certain philosophy holds sway on each outer plane, and that philosophy influences everything on the plane, including reality itself. There are 17 known outer planes, each corresponding to a major division in the AD&D alignment system. Sixteen of these planes form a great ring, with the plane of Concordant Opposition—the neutrality plane known as the Outlands—in the middle. New outer planes would probably form between two existing planes on the great ring or as additional “layers” on an existing plane.

The Prime Material Plane is where the base campaign and many similar worlds are located. There is a widespread misconception that there are multiple Prime Material Planes, sometimes referred to as Parallel Primes or Alternate Primes. In fact, there is only one Prime Material Plane. Within that plane, there are an infinite number of discrete worlds, each contained within a crystal sphere. A crystal sphere can contain a single planetary body, a whole solar system, or anything in between.

The Astral and Ethereal Planes act as highways between the other planes.

The Ethereal Plane connects the Prime Material with the Inner Planes. It resembles an infinite ocean whose “shores” lap against other planes. Curiously enough, ethereal travelers always find themselves moving toward the Inner Planes or their home world in the Prime Material. There is no known method of using the Ethereal Plane to travel from one Prime Material World to another.

The Astral Plane is an infinite, silvery void that connects the Prime Material Plane to the Outer Planes. Astral travel between Prime Material Worlds is possible.

Both the Astral and the Ethereal contain bits of solid matter in their depths. On the Astral, these form islands similar to asteroids floating in deep space where creatures make their homes. The Ethereal also contains islands, but they are called Demiplanes (see below) that exist as worlds in their own right.

For more information on the known planes, see the Planescape™ boxed set.

A Pocket Dimension is a discrete world attached to another world. These are usually very small, and most of their properties mirror those of the parent world. A Pocket Dimension can be created artificially.

A Demiplane is a discrete world floating in the depths of the Ethereal Plane. Like Pocket Dimensions, Demiplanes can be created artificially. Conditions on Demiplanes vary widely, and it is believed that large and well-populated Demiplanes can become full-fledged planes. The exact process for accomplishing this feat is not known to any mortal.

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