Climb Leap Ability : Complete Rosa's mission "Monkey See, Monkey Do" in Sequence 7 to earn the climb leap ability. With this ability, you can make longer jumps while climbing, letting you grab hand holds that'd normally be out of reach.
Disarm Combat Technique : Complete Mario's "Evasive Maneuvers" mission in Sequence 5 to unlock the disarm technique. Disarms let you counter incoming attacks from weapons that are normally too heavy to counter (like axes).
Unlock Condottiero War Hammer
Collect at least 50 feathers to unlock the Condottiero War Hammer.
Unlock Auditore Cape
Collect at least 100 feathers to unlock the Auditore Cape.