Volvagia

A legendary monster in Goron lore, Volvagia is the boss residing in the Fire Temple. The fierce, snake like dragon can only be killed with the legendary Megaton Hammer.

Some specualtion surrounding the beast is that it has some kind of relation to the Valoo, the guardian of the Rito. This is due to the coloring of the two creatures, and that they both, presumably, reside at the same location. (Dragon Roost Island, where Valoo lives, and Death Mountain, where Volvagia lives, are considered to be the same thing.)

In the OoT manga, Volvagia was Link's pet, but Ganon cursed it like Great Deku Tree and Gohma.