In the original Assassin's Creed, which Assassin is the playable protagonist during the Third Crusade?

Altaïr Ibn-La'Ahad is the playable protagonist of the original Assassin's Creed during the Third Crusade.

Altaïr is a Syrian Assassin and a master of the Brotherhood at the beginning of the game. After a failed mission causes him to lose his rank, his mentor Al Mualim sends him on a sequence of assassination contracts. These missions take Altaïr through major cities in the Holy Land, including Masyaf, Jerusalem, Acre, and Damascus.

The story is framed through the Animus, a machine that lets Desmond Miles experience the memories of his ancestors. Altaïr's campaign is therefore both a medieval adventure and part of the series' modern-day science-fiction narrative. He is sometimes confused with Ezio, who stars in the next mainline game, Assassin's Creed II. Altaïr also returns in Assassin's Creed: Revelations, where his later life is explored through memory sequences.