The Assassin's Creed protagonist who is a Medjay from Siwa is Bayek.
Bayek is the central character of Assassin's Creed Origins, which is set in Ptolemaic Egypt during the first century BCE. As a Medjay, he acts as a protector and law-enforcement figure connected to the traditions of ancient Egypt. His investigation into a series of killings leads him into a wider conflict involving the Order of the Ancients.
Bayek's personal story is closely tied to Aya, his wife and an important co-founder of the Hidden Ones. The game presents their activities as a foundation for the later Assassin Brotherhood, making Origins a chronological beginning for the organization's history within the series' fiction.
Aya is playable in selected sequences but is not the game's primary protagonist. Kassandra and Alexios are the selectable protagonists of Assassin's Creed Odyssey, which is set earlier in ancient Greek history. Bayek's title, Medjay, is therefore a key clue distinguishing Origins from the other ancient-world games.