Kassandra is the canon playable Eagle Bearer in Assassin's Creed Odyssey.
Odyssey lets the player choose Kassandra or Alexios as the playable character, but Ubisoft's later official material identifies Kassandra as the canonical Eagle Bearer. The game's story is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE.
Kassandra is a mercenary who becomes involved with the conflict between Athens and Sparta while investigating her family's history and the Cult of Kosmos. The open-world campaign includes mainland Greece, islands, naval travel, dialogue choices, and role-playing systems.
Alexios remains a valid player-selected protagonist within the game, which is why the question can be confusing. He is also used as Deimos, a major opposing character, when Kassandra is selected as the player character.