Shadows 2: Perfidia

I got a little bit panicked when this didnt unlock at the end of the game, you see, for this to unlock you need to go to the secrets menu and click on the UNLOCK button, then you will get the achievement.

The code to unlock and play this mini-game hidden in the Secrets menu is 0a355c90x

To unlock this achievement, you need to have had picked up the gun on Floor 2 in Michael's run.

The gun is found in the male bathroom by a corpse and a key.

Make sure to crouch at the end of Floor 1 (after picking up the last secret item on a nightstand there)

To get this achievement you need to complete the slender-man-eske secret mini-game accessed through the Secret menu. The code is 0a355c90x

The 8 pages are always in the same location:

1. In the smaller office opposite where you start - desk on the right.
2. In your office - directly across where you enter.
3. First room down the right hall - shelf in the far left corner.
4. Far left corner of the pool room.
5. Where the lockers usually are, at the end of the fork.
6. In the toilets - on the sink.
7. In the first room after locked door - shelf on the left.
8. In the second room after locked door - shelf at the back.
   The locked door is near the fork down the left hall. The key to unlock the door is near the elevator.
   After grabbing all 8 pages, you need to make it to the elevator to finish the game.