Bayek and Aya found the Hidden Ones in Assassin's Creed Origins.
The Hidden Ones emerge in the first century BCE after Bayek and Aya confront the Order of Ancients, a secret organization seeking political control in Ptolemaic Egypt. Their new group is designed to oppose tyranny while remaining concealed from the authorities and the public.
The Hidden Ones establish principles that later define the Assassin Brotherhood, including operating from the shadows, protecting ordinary people, and resisting domination. The game presents their early rules and symbols as the foundation for traditions seen in later historical periods.
The Order of Ancients is not the same organization as the later Templar Order, although the series presents it as a predecessor. Likewise, the Hidden Ones are the direct organizational predecessor of the Assassins, while Bayek's role as a Medjay predates the group's formation. Aya, who later uses the name Amunet, is also central to its development.