From the Super Mario Wiki
A Stumpet is an exceptionally rare and powerful enemy found in Barrel Volcano in Super Mario RPG: Legend of the Seven Stars. Stumpets seem to be formed from cooled magma which is shaped into a miniature volcano (which also resembles a tree trunk, which is probably what its name is derived from). Stumpets are apparently incapable of moving; despite this drawback, they are still a force to be reckoned with, as their Va Va Voom and Backfire attacks are almost unequaled in power amongst the game's normal monsters. Luckily, the attacks must be charged up for a turn (denoted by the Stumpet "getting furious!"), leaving the Stumpet open to attacks by the party.
Stumpets are capable of spewing Magmuses, enemies with high defense. This may mean that Magmuses are created by Stumpets or at least live in them, possibly meaning the two species may have a symbiotic relationship.
Among the unused sprites of Super Mario RPG: Legend of the Seven Stars, there is an enemy named Lumbler, which is a Stumpet lookalike. The only noticeable differences are that Lumbler is blue and has a different Moveset (which points to them probably being cut later than most cut enemies). The Moveset is Crystal and Birdo's Egg Shooting. Its psychopath thought is "Grrr!". Their name would have been a pun on "lumber," another name for wood.
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