Kassandra is Assassin's Creed Odyssey's canonical main protagonist.
Odyssey allows the player to choose between Kassandra and Alexios as the playable sibling. Ubisoft's official canon identifies Kassandra as the protagonist, while Alexios takes the role of Deimos in the main storyline. This distinction matters because both names can appear in discussions of the game, but they are not equally canonical in the broader series timeline.
The game is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. Kassandra is a mercenary of Spartan ancestry who becomes involved with political, military, and family conflicts across the Greek world. The map includes Athens, Sparta, the Aegean islands, and other regions.
Odyssey is set before the formation of the Assassin Brotherhood shown in Origins. Its connection to the franchise comes through the Isu mythology, the Cult of Kosmos, and the wider history of the First Civilization. Kassandra's story therefore predates Bayek's by several centuries.