Planes of Earth

In the negative planar sphere there exist a variety of planes entrenched in the energies of primal earth. While many planes contain skies of some sort, the realms of elemental earth rarely do - they tend to be difficult to tell apart, as many are simply vast caverns, cramped tunnels, and mountains. Native inhabitants of the planes of earth include the dao, xorn, and basilisk.
It is believed that the planes of earth are often in close conjunction with the material plane, and the tunnels of the underdark may lead across the planes.