Kassandra is the canon player character in Assassin's Creed Odyssey.
Odyssey allows players to choose either Kassandra or Alexios as the playable mercenary, but Ubisoft identified Kassandra as the canonical protagonist for the game's story. The character is a Spartan descendant who travels through the Greek world during the Peloponnesian War.
The adventure takes place in the fifth century BCE and includes Athens, Sparta, the Aegean islands, and other parts of ancient Greece. Historical figures such as Pericles, Socrates, and Hippocrates appear in the narrative, which combines real history with the series' fictional Isu mythology.
Alexios can still be selected by players and appears in the story in a different role. Deimos is the name used for the sibling who becomes an important antagonist in the family storyline, depending on the narrative perspective. Phoibe is a separate young character and ally, not one of the two playable options.