Rumblebump Volcano

From the Super Mario Wiki

Rumblebump Volcano is a place Luigi visits in Paper Mario: The Thousand-Year Door to retrieve a Marvelous Compass piece. He tells Mario that he met a giant stone-guardian with a weak spot at his head looking like a ruby, and that he threw his Blooper friend at it, which defeated the guardian. When Mario asks Blooey, though, he finds out that Luigi really missed and that the Blooper ended up in the magma.