Bayek of Siwa is the Medjay who becomes the central hero of Assassin's Creed Origins.
Bayek is a protector from the Siwa Oasis in Ptolemaic Egypt. After a devastating personal loss, he investigates a network of masked figures whose actions threaten Egypt. His journey helps explain the early formation of the Hidden Ones, the organization that later becomes the Assassin Brotherhood.
Aya, Bayek's wife, is also an important playable character and a major political figure in the story. The game therefore gives her substantial narrative importance, but Bayek remains the principal protagonist and the character most associated with the player role.
Senu is Bayek's eagle companion, not another name for Bayek. Origins also differs from earlier entries by emphasizing open-world exploration, role-playing systems, level progression, and a large Egyptian map.