Mysterious Key

The Mysterious key is a key that can be found in the Ruins's abandoned house, in the wardrobe of a bedroom. It can also be found at Azgore's Castle, in his room.

Both copies of the mysterious key do the same thing. It opens the outside and inside door of K-I007 Shelter, located in Iceland near the ammunition factory. Frisk will also need this key to open the bedroom of the Shelter, finding Mayah's remains along with her husband Zyriel and her daughter Zyrah, dead.