In the original Assassin's Creed, Altaïr Ibn-La'Ahad's mentor and target is Al Mualim.
Al Mualim leads the Assassin Order from Masyaf during the game's main story. After Altaïr breaks the Brotherhood's three central rules, Al Mualim demotes him and sends him on a sequence of assassination missions to regain his rank.
The name means “the Teacher” in Arabic and is also used as a title rather than a conventional personal name. The character is loosely inspired by Rashid ad-Din Sinan, the historical leader associated with the Syrian Nizari Ismaili community, but the game's Al Mualim is a fictionalized figure.
A common mix-up is confusing Al Mualim with Robert de Sablé, the Templar Grand Master who becomes one of Altaïr's major targets. Al Mualim's betrayal is revealed near the end of the story.