Technically, the visible universe that includes the Earth at its center, though only the Earth itself is known to have been explored by adventurers or communicated with by the gods. Called "Mother Earth" by the polytheists, or pagans, it is believed by the inhabitants of the Prime Material that Earth is also the center of the great tree Crann Bethadh, and that it emerged from the womb of creation (the roots of the Tree of Life) like a child being born from its mother. It is believed that the races upon the Earth emerged, one by one, directly from the Earth, given birth by the first great goddess, variously known as Ana, Anat and Anath. Likewise, it is believed that all the gods were also given birth by Ana, so that everything in existence, not just the Prime Material, came forth from her womb.

For most who have no religious convictions, the Prime Material simply "is" ~ all other planes of existence are largely imaginary, impossible to reach or the stuff of legends. "Reality," therefore, is Earth.

It must be understood that the laws of physics and all the principles of science can be counted on only to apply to the Prime Material Plane ~ and that magic, in all its forms, is a way that the counter-realities of other planes "leak" into the Earth sphere of reality. It is possible to travel from the Prime Material to other planes ~ but as the laws governing other planes often contravene what is familiar to most Earth creatures, it is generally considered dangerous to seek intra-planar travel.

See Mythology