What was the name of the first Assassin Brotherhood founded by Bayek and Aya?

Bayek and Aya founded the first Assassin Brotherhood as the Hidden Ones.

The Hidden Ones are established near the end of Assassin's Creed Origins, which is set in Ptolemaic Egypt. Bayek and Aya create the group after confronting the Order of the Ancients, a secret organization seeking political control through powerful leaders and institutions.

The Hidden Ones operate through secrecy, symbolic rituals, hidden blades, and a commitment to resisting domination. Their principles and methods form the early foundation of the Assassin Brotherhood seen in later historical periods.

The Order of the Ancients is not the name of the Assassin organization; it is the opposing faction in Origins and an ancestor of the later Templar Order. The Levantine Brotherhood belongs to a much later period, including Altaïr's time during the Third Crusade.