In the original Assassin's Creed, Masyaf is the Assassins' headquarters under Al Mualim.
Masyaf is a fortified mountain settlement in modern-day Syria and serves as the main base of the Assassin Brotherhood during the game's 1191 storyline. Altaïr Ibn-La'Ahad returns there between missions to receive instructions, report his progress, and obtain equipment. The fortress is governed by Al Mualim, the Brotherhood's elderly master.
The setting draws on the historical association between Masyaf and the Nizari Ismaili community, often popularly linked with the medieval “Assassins.” The game uses a fictionalized version of that history, blending real locations and figures with its own mythology about the Apple of Eden.
Masyaf is sometimes confused with the three major mission cities—Jerusalem, Acre, and Damascus. Those cities are destinations in the game, while Masyaf is the recurring home base and opening location.