Al-Mualim is the leader of the Assassin Order round the time of 1191. During the events of Assassin's Creed, he sets Altair on a quest of redemption by ordering the assassinations of 9 important figures from both sides of the conflict between Richard the Lionheart and Saladin during the Third Crusades, while re-instating Altair to his former rank.
Al Mualim is voiced by Peter Reneday.
Towards the end of game after assassinating Robert De Sable, it is revealed that Al Mualim was infact leading the 9 important figures under the Templar banner. And manipulated Altair into killing them so that he could keep the Piece of Eden for himself. Upon learning of Al Mualim's betrayal, Altair confronts his former Master in a fight to the death where soon after Al Mualim is assassinated allowing Altair to become the newly appointed master of the Assassin Order and owner of the Piece of Eden. In this last battle, Al Mualim uses the Piece of Eden to create duplicates of himself, which Altaïr must defeat in order to reveal the real Al Mualim. He also has a powerful attack that will take a large chunk of the player's health, if careless. Additionally, the Piece of Eden allows Al Mualim to teleport.
Assassin's Creed: Revelations
Through the keys Ezio Auditore Da Firenze finds, he is able to view stored memories left by Altair on the way to opening his vault. The first memory is set before the first game, in which Altair saves Al-Mualim's life before being granted the title of Master Assassin. The next memory recalls the ending of the first game and events that happen straight after in which Altair burns Al-Mualim's body (an act forbidden by assassins) to make sure that the corpse is not merely another illusion created by the Apple of Eden.