From the Super Mario Wiki
Muckles are large jellyfish-like creatures from Super Mario RPG: Legend of the Seven Stars. They were used by Valentina to guard the castle of Nimbus Land. Muckles are very large, actually bigger than Mario, and are capable of flight (or, at the very least, the ability to hover). These jellyfish can use powerful ice attacks such as Blizzard that hits all party members, or the powerful single-target ability Crystal. Muckles are capable of countering magic attacks with their own magic, but fiery attacks like Mario's Super Flame are quite effective. They have a resistance against most status effects as well. Muckle drops a valuable item, the Ice Bomb. Muckles are related to Leukos and may possibly be related to Jelectros.
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