Bayek and Aya found the Hidden Ones in Assassin's Creed Origins.
The Hidden Ones are created after Bayek and Aya confront the political and religious conspiracy known as the Order of the Ancients. Their goal is to oppose oppressive power while working from the shadows. The organization establishes principles and methods that later define the Assassin Brotherhood, including secrecy, selective targets, and resistance to domination.
Origins deliberately presents the Hidden Ones as a predecessor rather than using the later name immediately. The word “Assassin” is associated with a much later historical tradition, so the game frames its ancient organization as an early stage in the franchise's fictional history. This is why the Hidden Ones and the later Brotherhood should not be treated as identical names.
The organization's first headquarters is established at a desert location known as the Hidden Ones bureau. Aya and Bayek remain central to its formation, while other members help spread its ideas beyond Egypt. Origins was released in 2017 and was designed as a chronological origin story for the series' central conflict.