Fire Mountain (Mount Fry-Pan, or "Fry-Pan Mountain" in the viz manga) is a giant mountain ruled by the Ox-King
that is just outside the Diablo Desert.

A long time ago, the Ox-King had a wizard surrounding his castle with fire to keep intruders out, but the fire got out of control and even he was not able to get in. Oolong describes a common legend surrounding the mountain, saying: "Once upon a time it was 'Pleasant Mountain', and it live up to the name. But about 10 years ago, a fire spirit fell form the heavens and transformd it into a mountain of eternal flame... So they say."