Altaïr receives the title Mentor after becoming leader of the Assassin Order in Assassin's Creed Revelations.
Revelations presents Altaïr Ibn-La'Ahad as the Mentor of the Levantine Assassins. The game shows important stages of his life, including his return to Masyaf and his efforts to reshape the order after the events of the first Assassin's Creed. His leadership and reforms become part of the historical legacy later encountered by Ezio Auditore.
The title Mentor is an established leadership designation within the Assassin organization. It should not be confused with Master Assassin, which is used for ranks or advanced members in different contexts, or Grand Master, a title generally associated with Templar leadership.
Revelations is primarily set in Constantinople during the early sixteenth century, while its narrative also reaches Masyaf and uses memories connected with Altaïr. Ezio is the main playable character, but Altaïr's life and final years form a major part of the game's story.