A Dungeon Key is a secret item found in Castlevania: Lords of Shadow 2. They are used to open some secrets Dungeon Doors found in the game, that takes the form of a statue in a wall. They are dropped by Jailers, or can be purchased at the Chupacabras' shop.
In the deepest reaches of the castle, it is survival of the fittest. Killing for wealth is a constant in the lives of the dungeon clans, and turf wars are increasingly common. Only the guards have the means to forge crude metal keys, used to block access to their territory and keep their belongings out of covetous hands.