In Assassin's Creed Origins, the Medjay protagonist who investigates the Order of the Ancients is Bayek of Siwa.
Bayek is a protector from the Siwa Oasis in Ptolemaic Egypt. The game follows his investigation into masked enemies responsible for personal and political violence, gradually connecting his journey to the origins of the Hidden Ones.
Bayek's wife, Aya, is also a major playable character and an important founder of the organization that later becomes the Assassin Brotherhood. This relationship can cause confusion because both characters are central to the story, but Bayek is the game's primary protagonist.
The title's setting predates the historical name “Assassins.” Origins instead presents the Hidden Ones as the early form of the later Brotherhood, linking Bayek's personal quest to the series' larger fictional history.