In Assassin's Creed Odyssey, Kefalonia is Kassandra's childhood home.
The game opens with Kassandra living on Kefalonia, an island in the Ionian Sea. Her early life there introduces her family circumstances, her work as a mercenary, and the personal history that sends her into the wider conflict of the Peloponnesian War.
Kefalonia is also the player's first substantial region, with quests, villages, ruins, wildlife, and coastline to explore. Kassandra later travels throughout the Greek world, including Attica, Boeotia, Macedonia, and many islands, so the opening island is easy to confuse with other locations.
The historical Kefalonia is a real Ionian island west of mainland Greece. Odyssey takes creative liberties with its geography and chronology, but it uses recognizable Greek landscapes and political rivalries while presenting a fictional family story during the fifth century BCE.