In episode 3. You want to open the vault with no mistakes. You will need the water, air, fire, Earth, and love keys to do this. You can save prior to starting the puzzle in case you make a mistake. Interact with the vault. On the right there will be 4 key slots with symbols next to them. Numbering the slots 1-4 from top to bottom. 1 being the top and 4 the bottom. Use air key in 1, water key in 2nd, Earth key in 3rd, and fire key in 4th. You will need to interact with the keys in the correct order to get this in exactly 12 moves. The order is 1, 4, 2, 3, 2, 3, 1, 4, 3, 1, 2, 4. Done correctly, the achievement should pop there.