Go to the room were you make the old man potion in year four and go through the door to the right. In the room their is a gate with three locks on it. In the room their are three keys. To get the keys you will need Hermione, Griphook, and a Hufflepuff student (you can also use Dumbledore). To get the first key, go near the door where their is a picture with a man in it. Wave to the picture with the Hufflepuff student or Dumbledore and he will throw you a key. You can get the second key by making Griphook turn the key on the giant snake statue. The statue will move and drop the key out of its mouth. To get the third key you need Hermione to copy the pattern on the bookshelf. Once you have put the keys into the gate it will open and show some Lego bricks. Move the bricks to make stairs (going to the left). Once your done, go up and walk to the far left. Their is an open chest with Professor Snapes character token.