The Hidden Ones are the ancient Egyptian group that becomes the Assassin Brotherhood in Assassin's Creed Origins.
Bayek and Aya establish the Hidden Ones after confronting the Order of the Ancients, a secret organization seeking political control through powerful leaders. The group operates covertly and follows principles that anticipate the later Assassin creed, including resisting domination and protecting people's freedom of choice.
Origins presents this organization as an early form of the Assassins rather than using the familiar Brotherhood name from the start. The group's development explains how a personal struggle in Ptolemaic Egypt grows into an international clandestine movement. Their hidden blade and other traditions also receive historical context in the game.
The Order of the Ancients is the opposing organization, so it is a frequent answer choice but is not correct. In later historical periods, the Hidden Ones evolve into groups identified as Assassins, including the Levantine Brotherhood encountered in the first game.