Gleerok

Gleerok is the guardian of the Cave of Flames high atop Mount Crenel in The Minish Cap. It is the second major boss of the game, and it guards the Fire Element.

Strategy
Defeating the Gleerok involves firing the Cane of Pacci at its back, and then climbing onto its back and slashing with the sword while it is rendered unconscious. Gleerok's main form of attack is to spew fire on any surrounding prey or threats. If all else fails, it will submerge itself in its lava pool and cause major disruptions within its abode, including an increase in lava flow and tectonic disruptions that cause chunks of rock to fall from the ceiling. Gleerok seems to hold a same sort of power as the Fire Wizzrobe, as when the Gleerok spews fire, some of it causes Link to run around in a frenzy; the same thing that happens to Link if he is hit by a Fire Wizzrobe's power. Gleerok is most likely an evolutionary offshoot of the Gleeok, or a mutant/mutated Gleerok, adapted to harsh lava-filled environs. Along with this evolution/adaptation, it seems to have lost the ability to sprout multiple heads.

The Minish Cap manga
In The Minish Cap Manga, Gleerok was, prior to the battle, cursed by Vaati. Once defeated, Gleerok turns back to its true form, a softer, plesiosaur-like creature. The newly transformed Gleerok then gives Link the Fire Element.

Trivia

 * This creature bears an uncanny resemblance to the Pokémon Lugia, but only really in the facial area.
 * This boss is similar to Gohma from The Legend of Zelda: The Wind Waker. Both are fire bosses of fire dungeons that are variations of bosses that appear in other Zelda games and are fought by dropping a rock/rock-like structure on them.