Complete the indicated task to unlock the corresponding costume.

Altair's Grandmaster Robes (Old Eagle): Get 100% Sync in DNA Sequence 08.
Desmond Miles outfit: Complete all five of Desmond's DNA Sequences.
Master Assassin Robes: Complete the Assassins Guide challenges and become a True Master assassin.
Ishak Pasha Armor: Find all 10 Ishak Pasha Memoir Pages and complete the Hagia Sophia challenge level.