In Assassin’s Creed, Altaïr visits Masyaf first during the Third Crusade.
Masyaf is the mountain settlement that serves as the headquarters of the Assassin Brotherhood in the original game. Altaïr Ibn-La’Ahad returns there after an unsuccessful mission at Solomon’s Temple, where his actions lead to a serious demotion by Al Mualim, the Brotherhood’s mentor.
The game then sends Altaïr to several major cities in the Holy Land, including Damascus, Acre, and Jerusalem. Masyaf is different from those assassination targets: it is the Assassin stronghold and the place where missions are assigned, equipment is received, and story developments are revealed.
Masyaf is also a real historic settlement in modern-day Syria, associated with a fortress that later became connected in popular culture with the medieval Nizari Ismaili community. The game blends that historical setting with fictional characters and events.