Inner Planes

The Inner Planes surround and enfold the Prime Material Plane and its echoes, providing the raw elemental substance from which all the worlds were made. The four Elemental Planes—Air, Earth, Fire, and Water—form a ring around the Material Plane, suspended within the churning Elemental Chaos.
At their innermost edges, where they are closest to the Material Plane (in a conceptual if not a literal geographical sense), the four Elemental Planes resemble a world in the Material Plane. The Four Elements mingle together as they do in the Material Plane, forming land, sea, and sky. Farther from the Material Plane, though, the Elemental Planes are both alien and Hostile. Here, the elements exist in their purest form—great expanses of solid earth, blazing fire, crystal--clear water, and unsullied air. These regions are little--known, so when discussing the Plane of Fire, for example, a speaker usually means just the border region. At the farthest extents of the Inner Planes, the pure elements dissolve and bleed together into an unending tumult of clashing energies and colliding substance known as the Elemental Chaos.

Type

Planar Sphere/Grouping