The Hidden Ones are the secretive group that preceded the Assassin Brotherhood in Assassin's Creed Origins.
Bayek and Aya establish the Hidden Ones during the events of Origins. The organization is created to oppose the Order of the Ancients, a secret network that manipulates political power in ancient Egypt and serves as a precursor to the later Templar Order.
The Hidden Ones operate according to principles that anticipate the Assassin Creed, including protecting people from oppressive control and working from the shadows. Their early base is connected with the Egyptian setting before the organization expands beyond the region.
The name is distinct from the Assassin Brotherhood, which develops later in the series' fictional history. The Order of the Ancients is the opposing faction in this period, so it is not an alternate name for Bayek and Aya's organization.