Kassandra is the canonical protagonist of Assassin's Creed Odyssey according to the game’s novelization.
Odyssey is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. The player can choose to play as either Kassandra or Alexios, who are siblings. Both choices follow the same broad role as a Spartan mercenary, but the official novelization uses Kassandra as its protagonist.
This distinction matters because the game itself presents the choice as part of its role-playing design. Alexios is not an incorrect playable choice; he is an available player character. Kassandra is called canonical because the associated novelization and later franchise material identify her as the version used for the established storyline.
Odyssey explores the Cult of Kosmos, the player character’s family, and the wider Greek world. It is set centuries before the events of Assassin’s Creed Origins and does not focus on the later Assassin Brotherhood.