Which game introduced the fictional organization called the Hidden Ones in Assassin's Creed lore?

Assassin's Creed Origins introduced the Hidden Ones in Assassin's Creed lore.

The Hidden Ones are founded by Bayek and Aya during the events of Assassin's Creed Origins. They form a secret organization dedicated to resisting domination and protecting ordinary people. The group is presented as the historical precursor to the later Assassin Brotherhood, whose members and methods appear throughout the series.

Origins was released in 2017 and is set primarily in Ptolemaic Egypt during the first century BCE. Its narrative connects the organization’s creation to the death of Bayek and Aya's son, Khemu, and to their opposition to the Order of the Ancients. The latter group is the game's predecessor to the Templar Order.

The Hidden Ones are not identical to the later Brotherhood. Origins depicts an early stage in their development, including the creation of rules and symbols that become more familiar in later centuries. The term is also distinct from the historical Nizari Ismailis, whom popular culture sometimes labels “Assassins.”