Yusuf Tazim

Yusuf Tazim was the leader of the Assassin guild in Constantinople during the early 16th century. When the Mentor of the Assassins, Ezio Auditore da Firenze, arrived in Constantinople, a rivalry between Tazim and Auditore started - though the both of them learned from each other.

Source

 * Game Informer, June 2011 edition.