Kassandra is the canon protagonist choice in Assassin's Creed Odyssey.
Odyssey allows players to choose either Kassandra or Alexios as the playable character. Ubisoft's official modern Assassin's Creed lore treats Kassandra as the canonical protagonist, while the other sibling appears as Deimos, a major character in the story. The choice changes the player's point of view and character performance, but the broader historical setting remains the same.
The game is set in ancient Greece during the Peloponnesian War, beginning in 431 BCE. Kassandra is presented as a mercenary descended from Leonidas I of Sparta. Her story involves Sparta, Athens, the Cult of Kosmos, and the search for family members across the Greek world.
This fact is often confused because Alexios is equally available as the player's selected character and is prominently featured in promotional material and gameplay. “Canon” here means the version used by the wider official narrative, not that Alexios cannot be selected. The historical campaign is separate from the modern-day storyline involving Layla Hassan.