In the original Assassin’s Creed, Desmond Miles relives the memories of Altaïr Ibn-La'Ahad through the Animus.
Altaïr is the game’s principal historical character and an Assassin active during the Third Crusade. His missions take him across major cities in the Holy Land, where he investigates targets connected to the Templar Order. Desmond experiences those memories in a modern Abstergo facility, creating the series’ dual historical and contemporary narrative.
Altaïr begins the story as a highly skilled but overconfident Assassin. After a failed mission, he is demoted and must regain his rank by completing a series of assignments for his mentor, Al Mualim.
Altaïr is not the protagonist of Assassin’s Creed II; that role belongs to Ezio Auditore. Altaïr later appears in Assassin’s Creed: Revelations, which explores parts of his later life and legacy.