Reach level 50 in multi-player mode In Assassin's Creed: Brotherhood to unlock the Courtesan.

Unlock the following bonuses by collecting the corresponding number of Animus Data Fragments:

BONUS - NUMBER OF FRAGMENTS
Desmond Memory Sequence 1 - Collect 5 Fragments
Desmond Memory Sequence 2 - Collect 10 Fragments
Desmond Memory Sequence 3 - Collect 15 Fragments
Desmond Memory Sequence 4 - Collect 20 Fragments
Desmond Memory Sequence 5 - Collect 30 Fragments
Ishak Pasha's Memoir Pages appear on Map - Collect 25 Fragments
Animus Data Fragments appear on Map - Collect 50 Fragments
"Capped" trophy/achievement - Collect 100 Fragments

Unlock the following costumes by performing the corresponding tasks:

COSTUME - HOW TO UNLOCK
Altair's Grandmaster Robes (Old Eagle) - Get 100% Sync in DNA Sequence 08.
Desmond Miles outfit - Find 30 fragments and complete all the Desmond memory 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.

Unlock the following bonuses by performing the corresponding tasks:

BONUS - HOW TO UNLOCK
Altair's Sword - Complete the Set 3 Assassin Challenges.
Broadsword - Complete the Set 3 Mercenary Challenges.
Hired Mercenaries stop beggars - Complete the Set 2 Mercenary Challenges.
Hired Romanies poison guards - Complete the Set 2 Romani Challenges.
Hired Thieves pickpocket - Complete the Set 2 Thief Challenges.
Ottoman Mace - Complete the Set 3 Thief Challenges.
Romani Stiletto - Complete the Set 3 Romani Challenges.

Unlock the following cheats by performing the corresponding tasks. Select the cheats at the "Options" menu during the replay of a memory:

CHEAT FUNCTION - HOW TO UNLOCK
Buns of Steel - Get 100% Sync in DNA Sequence 02. This cheat makes you immune to all forms of damage.
Calling All Assassins - Get 100% Sync in DNA Sequence 05. This cheat gives you unlimited use of the Assassin bars.
Infinite Ammunition - Get 100% Sync in DNA Sequence 07.
Killing Spree - Get 100% Sync in DNA Sequence 03.
Permanent Secrecy - Get 100% Sync in DNA Sequence 06.
The Old Eagle - Get 100% Sync in DNA Sequence 08.
Ultimate Guild - Get 100% Sync in DNA Sequence 04. This cheat makes all assassins become Master Assassins.