Kassandra is the playable Greek protagonist in Assassin's Creed Odyssey's canon storyline.
Odyssey lets players choose either Kassandra or Alexios as the playable mercenary. Ubisoft's stated canon for the game's broader Assassin's Creed continuity identifies Kassandra as the protagonist, and later material follows that version of events.
The story takes place during the Peloponnesian War in the fifth century BCE. Kassandra travels through the Greek world, becomes involved in family conflicts and political struggles, and investigates the Cult of Kosmos.
Alexios remains a valid player-selected protagonist within the game, which is why answers can vary if a question asks only who can be played. The word “canon” is important here: it distinguishes the officially continued version from the player's choice in an individual playthrough.