Fastest way to get Ghost Armor Achievement.
When you start a new game, you play until you meet a metal soldier, then you kill him and see if he gave a part to the ghost Armor.
If you dont get good droop just click ESC and Back To Menu. Then click continue and bum you start again the same section where the old knight is alive.
You repeat everything until you receive the desired item. It took me about an hour; P Greetings.