Octogon is the Boss of the Mermaid's Cave in Oracle of Ages. It can spit rocks like its relatives, the Octoroks, and does so when above the water. It bears a resemblance to the Big Octo that appears in Ocarina of Time.
Octogon is fought in a room full of deep water with a small piece of floor to stand on in the center of the room. To defeat Octogon, Link must first stand on the floor and wait for Octogon to turn and attempt to fire a rock. Link can then attack the rock with his Sword or Seed Shooter to prevent it from hitting him. After a while, Octogon will flee beneath the water. Link must follow it by diving with the Mermaid Suit and attack it until it is defeated. Following its defeat, Link will receive the fifth Essence of Time, the Lonely Peak.