Bayek of Siwa is the Egyptian Medjay protagonist of Assassin's Creed Origins.
Bayek is a protector of the Siwa Oasis and one of the last Medjay, an ancient Egyptian title associated with guardianship and royal service. The game follows his investigation into a conspiracy that affects his family and draws him into the beginnings of the Hidden Ones.
Origins is set in Ptolemaic Egypt, during the first century BCE. It presents cities, deserts, tombs, and monuments across a large open world, while incorporating historical figures including Cleopatra and Julius Caesar. Bayek's wife, Aya, is also a major character and an important participant in the formation of the Hidden Ones.
The Hidden Ones are the organization that later develops into the Assassin Brotherhood. Bayek is therefore not simply a later member of the established Brotherhood. The series uses Origins to depict the movement's beginnings, which is why the game functions as a story about origins as well as a historical adventure.