The playable Assassin in the original Assassin's Creed game is Altaïr Ibn-La'Ahad.
The game is set mainly in the Holy Land during the Third Crusade, in 1191. Altaïr is a senior member of the Levantine Assassins, but his rank is temporarily reduced after he breaks the Brotherhood's principles during an early mission. His subsequent assignments take him through cities including Masyaf, Damascus, Acre, and Jerusalem.
Altaïr's story is framed through Desmond Miles, whose genetic memories are accessed by the Animus. This narrative device connects the historical setting to the modern-day plot and became a defining feature of the series. Altaïr is sometimes confused with later protagonists such as Ezio Auditore, but Ezio leads the Renaissance-era games beginning with Assassin's Creed II. Altaïr also returns in Assassin's Creed: Revelations, where his later life and legacy are explored.