We are legion

Answer the call for help

Complete one combat challenge without taking damage (any character)

Last man standing

Solve the first riddle

Drop in on an old friend

There is only one way in

Save the damsel, but is she in distress?

Viewed all flashbacks.

Obtained all weapons (excluding weapons obtained via password).

Used overhead view on Shadow Moses Island.

Killed many enemies in one area, and vomited.