Material Prime. This plane is the core reality of D&D. This is
where adventurers slay merciless dragons, rescue helpless damsels, and drink
themselves into a well-deserved stupor.
Lands of Orcus. A war torn Material Plane where the armies of
Orcus hold power. There are many similar areas mirroring this plane and
the Prime, often resulting in some interesting "Dark Mirror" plot lines.
A new round of wars has recently started here, apparently backed by wizards
awakened from the distant past
Lands of Ice. An icy frozen world, windy and bitterly cold, sunless, and
inhabited mostly by a race of deadly and evil Ice Titans. Iuz holds sway in this
place.
Demi Planes
Citidal of the Dying King. A soul sucking desert surrounding a skull shaped
citidal where Vecna used to live, before he escaped this prison plane. Travel
to this plane can be risky, as the borders can close behind you leaving you trapped.
Lands of the Raven. A very tenuous series of small demiplanes that border
on each other in a very unstable manner. Some of these places have an unnerving
habit of winking out of existance, the fates of the inhabitants is unknown.
Travel here is also not suggested, as the borders are notoriously hard to
penetrate.
Transitive Planes
Astral Plane is the plane used with
teleportation effects. It is a vast expanse that surrounds the Material Prime.
Astral projection does not work here as it does in other worlds, but physical
access is fairly easy, as all you have to do is fly high enough.
Ethereal Plane is the plane where ghosts and other immaterial creatures
reside. This is also sometimes known as the Plane of Shadow (they are the same
plane in this cosmology). The plane of shadow is a hazardous plane. As
you might suspect from its nature, it is filled with features that resemble
those found on the prime material plane, but dark and twisted.
Energy Planes
There are two enormous sources of energy that server as the
power sources of the multiverse. Postive Energy.
Negative Energy.
Material Planes
Elemental Air.
Elemental Fire. Access to the elemental plane of fire is fairly simple,
one can find gateways in volcanos, or fly up to the sun.
Elemental Earth.
Elemental Water. Gateways to the elemental plane of water are found in
the deepest trenches of the Material Prime.
Outer Planes
The Great Wheel cosmology is based around the twin axes of good-evil and
law-chaos. The cardinal points
are occupied by the plane of purest good (Elysium) opposite the plane of purest
evil (The Grey Wastes), and the plane of purest law (Mechanus) opposite the
plane of purest chaos (Limbo). Between each of these are a trio of planes moving
in ideology between them. Overall, they are arrayed as follows:
Abyss (A balance of Chaos and Evil, home of the demons)
Acheron (lawful, but faintly tainted by evil, showing many of the worst parts of an excess of order)
Arborea (Vast expanses of wilderness balancing the wild Chaos of nature with its nurturing Goodness)
Arcadia (A place where Order reigns supreme for the common Good)
Beastlands (A somewhat friendlier wilderness, filled with giant, intelligent animals)
Bytopia (A Good plane which promotes Law as far as it supports the greater Good)
Carceri (Evil, with a bit more wildness thrown in, prison plane of the multiverse)
Celestia (A plane of Law and Good, every Paladin's dream)
Elysium (A realm of pure Goodness, so pleasant that it can be hard to leave)
Gehenna (More evil than lawful, and expanse of uneven volcanic slopes)
Grey Waste (A place of pure evil, effectively neutral evil)
Limbo (Chaotic neutral, a churning plane of pure Chaos)
Mechanus (effectively lawful neutral, a place of clockwork and perfect order)
Nine Hells (effectively lawful evil, home of the devils.
Pandemonium (A madhouse of shrieking winds showing the worst parts of Chaos)