The Guttermouth Key is a monster drop that can be found in the Nightmare. It can be found from various sources and locations throughout the Nightmare including but not limited to:
- A rare drop from a Boomer.
- A rare drop from a Goon.
- A rare drop from an Industry Giant.
- A rare drop from a Macabre Candelabra.
- A rare drop from a Red Wolf.
- A rare drop from Democan.
- A very rare drop from a Data Mite.
- A very rare drop from a Flying Clown.
In appearance, the Guttermouth Key is a blackish-purple key with a worn look. The Guttermouth Key is used to unlock doors sealed with the keylocks that can only be opened by the Guttermouth Key. After a player had unlocked and entered a Guttermouth Cell, they may participate in different Guttermouth challenges with different mobs throughout the Nightmare for rewards. After the Guttermouth Key is used once, it will be disappear from the player's inventory. If the player has no purpose for the Guttermouth Key, it can be sold for 10,000 gold.