Bouldergeist

Bouldergeist is a boss in the game Super Mario Galaxy. Its name is a portmanteau of boulder and poltergeist. It is the boss of the Ghostly Galaxy, and was destroyed by Mario in battle.

Appearance
Bouldergeist is essentially a huge column of rocks roughly shaped into a face. However, its real form is a more extreme version of a Bomb Boo, with what could be its uvula, tongue or heart hanging from the bottom. It has two enormous stone hands, which are used only in the second half of the battle. Bouldergeist's attacks include tossing rocks at Mario, summoning lines of stalagmites from the floor, and in the second half of the battle, slapping his hands on the ground and punching at Mario. It is fought in a plain circular arena.

Combat
To defeat Bouldergeist, Mario must swing Bomb Boos into it. To get Bomb Boos, dodge the black rocks that he throws at you. Once they hit the ground, they will turn into Bomb Boos. Each hit will gradually cause Bouldergeist to lose a bit of its stone layer. Three hits will completely destroy the entire stone layer surrounding Bouldergeist's real form. Once this happens, Mario has to, yet again, spin a Bomb Boo at the shadow's red bubble to inflict more damage on Bouldergeist. However, the fight is not over, as Bouldergeist regains its old stone layer, and reveals its large rock hands. Bouldergeist then has a greater variety of attacks, as well as a larger form of protection. Mario can, however, destroy the hands the same way, but they regenerate after a short time, so Mario has to damage Bouldergeist before the hands reappear again. Mario must once again swing three Bomb Boos into it, and then swing one final Bomb Boo into its shadow form to defeat the malevolent stone creature and claim his Power Star. Also, in the second round, Bouldergeist may shoot golden rocks which reveal a coin.

Later, Mario must defeat him with one wedge of health under the Daredevil Comet to claim the spectre's second star. Bouldergeist will no longer throw golden rocks.

Trivia
He also bears a striking similarity in moves and appearance to Shifting Sands Land's boss, Eyerok, from Super Mario 64 and Super Mario 64 DS.They both push and punch the character with their huge, stone hands and both are destroyed with around 6-8 hits.
 * The theme music while fighting Bouldergeist is the same as Kingfin's theme music.
 * Bouldergeist closely resembles Bogmire from Luigi's Mansion, as they have the same mouth and eyes. They are both ghosts, as well.
 * Bouldergeist is named after a poltergeist, a very dangerous form of ghost who throws things, possibly a reference to his boulder throw attack.
 * Bouldergeist is extremely similar to Cackletta's soul, as they both look similar and the battle is also similar. The player must destroy both of their body parts to reveal a "heart" and destroy that.