Hades is the primary antagonist in the anime series 'Saint Seiya.' As the god of the Underworld, he is one of the most powerful deities in the series, often opposing the protagonists, the Saints of Athena. His character is portrayed as cold, calculating, and driven by a desire to plunge the world into eternal darkness. Hades is a central figure in the Hades arc of the series, where he commands an army of Specters and battles Athena and her Saints across various realms, including the Underworld and Elysion.