From the Super Mario Wiki
King Calamari is a giant Blooper, and is a minor boss encountered in Super Mario RPG: Legend of the Seven Stars. It sank Jonathan Jones' ship (as chronicled in various logs found throughout the vessel) and was locked in the treasure room. Mario had to work out a six letter word before he can enter the treasure room using clues provided in various rooms of the ship. This word is "pearls" and after Mario works it out, King Calamari allows him in the treasure room, where it is battled as a boss.
After defeating King Calamari, Mario and his allies gain access to the lower section of the sunken ship.
When battle starts, the player must destroy two groups of three of King Calamari's tentacles before facing against King Calamari's main body and two other tentacles. The tentacles attack by either slamming a party member or throwing one high into the air. The latter attack does not reduce a party member's HP, but it induces the Fear status effect, even if the target would normally be immune to Fear. Even if King Calamari is defeated, the remaining tentacles need to be destroyed to finish the battle.
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