In Hades, we explore Greek mythology by travelling through different biomes and fighting various bosses. Zagreus would fight and defeat them in the following order:

  1. In Tartarus: one of the Fury Sister, Megaera (or even all 3 of them at high heat)
  2. In Asphodel: the Bone Hydra
  3. In Elysium: Theseus, the former king of Athens, and Asterius, the Minotaur
  4. In Temple of Styx: Ceberus, the three headed hell hound
  5. On the “Surface”: Hades, the god of the Underworld
spoiler

Um actually … you do not need to fight Ceberus in the Temple of Styx. Zagreus is tasked to retrieve a Satyr Sack to placate the hound to let him through.