Kassandra is the selectable sibling identified as the main character in Assassin’s Creed Odyssey’s canon story.
Assassin’s Creed Odyssey lets players choose between Kassandra and Alexios at the beginning of the game. The player’s choice changes the on-screen protagonist, but official supplementary material, including the novelization, identifies Kassandra as the canon Eagle Bearer. Alexios instead has a major role as Deimos, a character central to the Cult of Kosmos storyline.
Odyssey was released in 2018 and is set during the Peloponnesian War in fifth-century BCE Greece. The campaign includes Athens, Sparta, the Aegean islands, and other regions of the Greek world. Kassandra is a descendant of Leonidas I of Sparta and carries the broken Spear of Leonidas, an important artifact in the story.
This distinction can cause confusion because both siblings are playable in the game itself. The answer refers specifically to the canon version of the protagonist, not to every player’s chosen character. Odyssey is also separate from Origins, which follows Bayek in ancient Egypt.