Easily missable, save on your first visit to Darvin's Village. You can get this achivement just before you enter the only building on Darvin's Village map, be aware that if you have Rose in your party she will open the door for you prevening you from gettin Sinister Legacy achivement so save before the door and dismiss her. The code for the door is PROTEUS (7768387), after putting it in you will get the achivement. If by any chance game wouldnt give it to you the code can be learnt in the Rangers Citadel's museum by inspecting Finster's head.