“The Underdark? A child’s toybox compared to the twisting labyrinths, caves, passages, and wonders of the Plane of Earth. In the Underdark, there’s an innate sense of the world above that colors the experiences of travelers and inhabitants, but this does not exist on the Plane of Earth. It is suffocation and brutality defined and stands as one of the least hospitable of the Inner Planes. Still, the realm is ripe with treasures and secrets buried beneath the rock and stone.”
Ezoviar Gwyn, planar scholar
Earth symbolizes stability, rigidity, stern resolve, and tradition. The plane's position opposite the Plane of Air in the ring of the Elemental Planes reflects its opposition to almost everything air represents.
The Plane of Earth is a titanic sprawling complex of tunnels and caves created both from natural effects and deliberate hands. The caves are filled with stalactites and stalagmites, though water is a rare sight – what then creates these natural formations? No one knows the answers for sure, and most simply believe they rise and fall from the will of the plane itself.