It does not attack offensively, but rather attempts to steal gil from the party, as its name implies. Once it successfully steals, it escapes on its next turn, taking the gil with it. As with most enemies in Mt. Zozo they have high Evasion, so (if playing the GBA port; see below) magical attacks are advised, particularly Fira. Dispatching them before they can flee will earn back any gil they stole at the end of the battle.
Because of the Evade bug in all versions of Final Fantasy VI apart from the GBA port, Mugbears were much easier to dispatch than intended.
The Japanese name for this enemy is based on the English and grammatically curious "Stolen Bear", referring to the enemy's ability to steal from the party. The English name "Mugbear" uses a different word related to stealing and serves as an added pun on the word "bugbear". [view·edit·purge]A bugbear is a legendary creature or type of hobgoblin comparable to the bogeyman and other creatures of folklore historically used to frighten disobedient children. The name is derived from a Middle English word bugge (a frightening thing), or perhaps the old Welsh word bwg (evil spirit or goblin), or old Scots bogill (goblin). In medieval England, the bugbear was depicted as a creepy bear that lurked in the woods to scare children. In a modern context, the term serves as a metaphor for something annoying often with a connotation that the loathing it inspires is disproportionate to its importance.