Prime Material plane

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

There is supposedly 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 is located. However, in the cosmology shared by the Planescape and Spelljammer campaign settings, there is only one material plane (called the Prime Material Plane), which contains the crystal spheres of many different worlds separated by the Phlogiston.