The "Man Shaped Key" is really the dummy gun. If you go up to the door with the "Man Shaped Key" in Fate Tower, bring your dummy gun. Shoot the dummy gun at the door. The door should open and will take you to the final room in Fate Tower. Note: You must repeat this every time you leave Fate Tower and re-enter it. If you have already completed Fate Tower you do not need to do this. This will lead to the same room where you fought the final Boss.