Inside The Narzissenkreuz Ordo, there is an Exquisite Chest that gives ‘Key to Some Place in the Institute.’ By reaching the location, you will get a Precious Chest and a hidden achievement ‘A Study in Sable.’
➥ If you didn’t get the key yet, teleport to the book icon in the Institute of Natural Philosophy and enter the Narzissenkreuz Ordo. Read the guide here if you don’t know how to reach the Narzissenkreuz Ordo.
➥ Inside the Narzissenkreuz Ordo, there is an Exquisite Chest just beside a Precious Chest. Claim the chest and you will get the ‘Key to Some Place in the Institute.’
➥ After you get the key, teleport to the Institute of Natural Philosophy waypoint (right near the wording) and swim in the water that leads to the northeast.
➥ When you reach land again, turn right (south) and you will see a closed door with a mechanism in front of it. Interact with the mechanism and use the key to unlock the door.
➥ Inside the door is yet another door but this one is not locked and you can just interact with the mechanism to open the door. You will get the hidden achievement ‘A Study in Sable’ after opening the door.
➥ Inside the room is the mud from the Chasm that we can’t interact with and a Precious Chest. There’s also Enigmatic Page (V) on top of the table.
➥ At the end of the room is another door, and you can interact the mechanism to open it and unlock a shortcut to the underwater waypoint.