Kaiou Poseidon is the god of the seas in Saint Seiya, serving as the main antagonist of the Poseidon arc. He awakens to punish humanity with floods and to cleanse the world through overwhelming oceanic power. As one of the series' most powerful divine beings, he commands the Mariners, the seven Sea Generals, and rules from his underwater temple. His role is both cosmic and mythic, embodying divine judgment, nature's wrath, and the danger of absolute power.