Main Hall Key
From WikiRaider
The Main Hall Key is a key found in the level Barkhang Monastery in Tomb Raider II.
It is found on a platform in catwalk above the Main Hall of the Barkhang Monastery. Even though you're above the Main Hall once you claim the key, dropping to below is a deadly fall.
The key unlocks the main door, and safe way, to the Main Hall of the monastery.