Kassandra is the canonically established protagonist of Assassin's Creed Odyssey.
Odyssey allows players to choose between Kassandra and Alexios at the beginning of the game. Both choices follow the same broad narrative structure, but official later material and series continuity identify Kassandra as the canonical Eagle Bearer.
The game is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. Kassandra is a mercenary descended from the Spartan king Leonidas I and becomes involved in family conflicts, political struggles, and the activities of the Cult of Kosmos.
Alexios remains a valid playable choice within the game itself, which is why the answer can appear ambiguous when discussed without the word “canonical.” Phoibe is Kassandra's young companion, while Aspasia is an important historical and narrative figure rather than the protagonist.