Bayek of Siwa is the protagonist who leads the Hidden Ones in Assassin's Creed Origins.
Bayek is a Medjay from the Siwa Oasis in Ptolemaic Egypt. Alongside Aya, he investigates the forces responsible for personal tragedy and discovers a wider conspiracy involving powerful figures. Their work eventually contributes to the creation of the Hidden Ones, the organization that later develops into the Assassin Brotherhood.
The game is set primarily in Egypt during the first century BCE, before the Brotherhood uses the familiar Assassin name. Bayek's title as Medjay reflects an ancient Egyptian protector role, while his travels take him from desert settlements to major cities such as Alexandria and Memphis.
Aya is essential to the story and is playable in selected sequences, but Bayek is the principal protagonist. Kassandra belongs to Odyssey, and Basim is associated with Valhalla and Mirage, making those names common points of confusion.