In Assassin's Creed Origins, the protagonist who protects Siwa is Bayek of Siwa.
Bayek is a Medjay, an elite protector and lawkeeper in ancient Egypt. His connection to Siwa is central to the opening of the game and to his identity. After a personal tragedy, he begins pursuing masked figures whose actions gradually reveal a wider conspiracy connected to the origins of the Hidden Ones, the organization that later becomes the Assassins.
Bayek's wife, Aya of Alexandria, is also a major character and an important ally. Because both characters are playable at different points, some summaries describe Aya as a co-protagonist. The game's primary player character and narrative viewpoint, however, is Bayek.
Origins is set during the first century BCE, in the final period of Ptolemaic Egypt. Its world includes Alexandria, Memphis, Cyrene, the Sinai, and the Great Sphinx. The game was released in 2017 and serves as an origin story for the Assassin Brotherhood's earliest known form.