The Prime Material Plane

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

"You want to know of the Prime, visit it. The boundless worlds of that plane have an infinite variety, as do the planes, but I cannot encapsulate them as I have here. Suffice it to say they are the birth of the Outer Planes, the children of the Inner, and they hold limitless potential within their boundaries." — The spirit Asonje.