Kephallonia is the childhood home island of the playable protagonist in Assassin's Creed Odyssey.
The 2018 game begins on Kephallonia, an island in the Ionian Sea. The player chooses either Kassandra or Alexios as the main character, and the opening chapters establish the protagonist's family history, local relationships, and mercenary life before the adventure expands across the Greek world.
Kephallonia is based on the real Greek island of Kefalonia, although the game uses the spelling Kephallonia in its fictionalized ancient setting. The island serves as an introductory region rather than the entire setting. Later exploration reaches many parts of the Aegean and mainland Greece during the fifth century BCE.
Kassandra and Alexios are alternate player-character choices, so a question asking for one protagonist alone can be ambiguous. The island, however, remains the same starting home in the game's main story regardless of that selection.