Cephalonia is the Greek island where Kassandra or Alexios begins Assassin's Creed Odyssey.
The protagonist is raised on Cephalonia after being cast from Mount Taygetos as a child. At the start of the game, the player character works as a misthios, or mercenary, on the island before accepting a contract that leads into the wider Peloponnesian War.
Cephalonia is a real Ionian island west of mainland Greece. In the game, its settlements, cliffs, beaches, caves, and surrounding waters introduce exploration and naval travel.
Odyssey later expands across a large fictionalized version of the Greek world, including Attica, Lakonia, Phokis, Naxos, and Crete. Naxos is particularly important to the family story, but it is not the starting island.