Bouldergeist

Bouldergeist is a boss in the game Super Mario Galaxy. Its name is a pun on boulder and poltergeist. It is the boss of the Ghostly Galaxy, and may or may not be based on Eyerok from Super Mario 64.

Appearance
Bouldergeist is essentially a stone column with a face, however, its real form is a black ghost-like creature, with a red bubble underneath it. He has two enormous stone hands, which only appear in the second half of the battle. Bouldergeist's attacks include tossing rocks at Mario, summoning lines of spiky rocks from the floor, and in the second half of the battle, slapping his hands on the ground and punching at Mario. He is fought in a plain circular arena, which is walled off by small stone blocks.

Combat
To defeat Bouldergeist, Mario must swing Bomb Boos into him. 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 (see Appearance), 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.