Kassandra is the canonical protagonist of Assassin's Creed Odyssey according to the game's official storyline.
Odyssey allows players to choose either Kassandra or Alexios as the playable mercenary. The selected character becomes the Eagle Bearer, but Ubisoft's established canon identifies Kassandra as the protagonist whose story continues into later Assassin's Creed material.
The game takes place in ancient Greece during the Peloponnesian War, beginning in 431 BCE. Kassandra travels through the Aegean world, confronting political factions, the Cult of Kosmos, and members of her divided family. Her choices affect many conversations and outcomes without changing the character's canonical identity.
Kassandra is also connected to the Staff of Hermes Trismegistus. In the modern-day storyline, she gives the staff to Layla Hassan and is shown to have lived for centuries through its power before dying in 2018. Alexios remains a valid playable choice, which is why the two names are often confused.