Prime Material Plane

The Material Plane, more usually called "the mortal world", existed between the two opposing fundamental planes: the Astral Plane, commonly called the Astral Sea, and the Elemental Chaos.

The Prime Material plane was also connected to the Astral Plane, which served as a conduit to the Outer Planes. There was no known direct way to travel between the Inner and the Outer Planes, or between the Astral and the Ethereal, that did not pass through the Material Plane first. Similarly, the Prime was the only plane in which spells that required a connection to the Ethereal or the Astral both worked.

Being the only plane that intersected both the Ethereal and the Astral, the Prime Material plane occupied an important position as a crossroads of the multiverse, and all other planes were defined in relation to the Prime.