Prime Material plane

The Prime Material plane (also seen as Prime Material Plane) was the plane in which Toril and the surrounding cosmos existed. The phrase "Prime Material plane," or simply the "Prime," was generally used by beings from other planes in the Forgotten Realms cosmology (notably Sigil), and "prime" was used by the same beings to refer to the inhabitants of Toril.

At first it was thought that there was an infinite number of material planes, among them the Prime Material plane, the Abeiran material plane, Oerth's material plane, Krynn's material plane, and the universe in which Earth was located. However, by the mid-14 century DR, it was generally accepted that there was only one material plane (called the Prime Material plane), which contained the crystal spheres of many different worlds separated by the phlogiston.