Octogon

Octogon is the boss of Mermaid's Cave in The Legend of Zelda: Oracle of Ages, appearing in the past version of the dungeon. It is a giant shelled Octorok resembling a Big Octo, able to attack from both over and under the surface of water.

Octogon's room is made up primarily of water with a narrow floating island in the middle. When Link is on the same level as Octogon, it will attack him directly; otherwise, it will launch energy balls from the hole in its shell, which rain down and split into four small ones, rapidly moving outwards in either the cardinal or ordinal directions. Every so often, it will change its position, and will do this sooner when attacked enough. While on the surface, Octogon moves back-and-forth around the island with its shell facing inwards, occasionally stopping to turn around and spit a rock. When underwater, it swims after Link, occasionally turning around to spit a bubble to trap him, though these can be popped with any available attack. In both cases, Octogon can be attacked directly easiest when it turns around to keep the shell from guarding it, though a bouncing attack from the Seed Shooter can hit it otherwise. After enough damage, Octogon explodes, with the Heart Container appearing on the island.