Key (Watcher's Keep Altar Level)

The Key is not labelled nor has any clue as to what it is for.
==Location==
The key can be found inside a cabinet in one of the rooms on the Watcher's Keep Altar Level, closest to the Southeast section of the map .
==Description==
==Gameplay==
There is no clue given in the game as to what this key is for.
A "spoiler" reveal button is below for readers who want to know the answer to this key. Don't read it if you desire to figure it out on your own as intended for a first-time player.
The key will open the only locked door (a door which cannot be forced or opened otherwise) on this dungeon level, which is labelled with the Automap marker "The Priest's Crypt" . The door to the Crypt will display - "This magical lock will only open for a specific key. No amount of tinkering will help.", unless this key is possessed.