Yusuf Tazim

Yusuf Tazim was the Grand Master of the Ottoman Assassins, operating primarily in his hometown of Constantinople. He was involved in the fight against the Byzantine Templars during the early 1510s, and in aiding Ezio Auditore da Firenze - the Mentor of the Italian Assassins - during his search for the Keys of Altaïr.

In the process, he and Ezio managed to form good relations with the Ottoman Royal House, particularly Şehzade Suleiman and Şehzade Ahmet. Together, they thwarted the Templars' plans to take over the Ottoman Empire and found the Keys hidden in Constantinople.

Early life
Yusuf was born in Constantinople, the heart of the Ottoman Empire, at that time known as the "Crossroads of the World." Raised to be an Assassin from birth, he rose through the ranks to eventually become the Mentor of the Ottoman Assassins by 1511.

Meeting Ezio Auditore
In 1511, Yusuf met fellow Mentor Ezio Auditore, who arrived at Constantinople in search of the Seals of Altaïr. Yusuf showed Ezio around the city, giving him a hookblade in the process and introducing him to the various types of bombs that the Ottoman Assassins used.

Together, they climbed the Galata Tower, and viewed the city from above, before both leaving it by performing a Leap of Faith.

Rescuing Suleiman
That same year, Ezio and Yusuf infiltrated Topkapı Palace dressed as entertainers, so as to join the party held for Prince Suleiman, who was in danger of a Templar assassination. Ezio and Yusuf were able to find the disguised Templars and have the Ottoman Assassins silently kill them.

Appearance
Yusuf wore tan Assassin robes and a headband, both with teal sashes. He wielded a hidden blade, the hookblade, and throwing knives.

Source

 * Assassin's Creed: Revelations