Kassandra is the sibling of Alexios in Assassin's Creed Odyssey.
Odyssey lets the player choose either Kassandra or Alexios as the playable protagonist. The selected character is a Spartan mercenary and the other becomes the sibling known in the story as Deimos. Kassandra is the canon protagonist in the wider franchise continuity, although both choices are playable within the game itself.
The adventure is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. It includes Athens, Sparta, the Aegean islands, and many other locations. Kassandra's family story intersects with the Cult of Kosmos, a secretive organization influencing Greek politics. The game was released in 2018 and is not a direct retelling of a known historical life. Its player choices can alter relationships and outcomes, but the central sibling identities remain tied to the selected protagonist.