In the first Assassin’s Creed game, Masyaf is home to Altaïr Ibn-La’Ahad in 1191.
Masyaf is a mountain settlement in modern-day Syria and serves as the headquarters of the Assassin Brotherhood during the game’s opening chapters. Altaïr returns there after missions and receives instructions from Al Mualim, the Brotherhood’s leader.
The game also features three major cities: Jerusalem, Acre, and Damascus. Those cities are mission locations, so they are sometimes confused with Masyaf. Masyaf is different because it functions as the Assassins’ base rather than as one of the principal urban districts that Altaïr investigates.
Historically, Masyaf is associated with the Nizari Ismaili community and with Rashid al-Din Sinan, a leader later known in European sources as the Old Man of the Mountain. Assassin’s Creed uses that historical setting as the foundation for its fictional Brotherhood story.