Heracles, known by his class name Berserker, is a powerful Servant in the anime series Fate/stay night. He is summoned by Illyasviel von Einzbern and is famous for his immense strength, endurance, and combat abilities, fitting for his legendary status as the Greek demigod Heracles. As Berserker, he is driven by madness, which greatly enhances his power but limits his ability to reason. He serves as a formidable opponent to the main protagonists in the Holy Grail War.