The Water Prison Generator Room Key is a key that must be picked up in Silent Hill 4: The Room. Unlike the other keys in the game, Henry Townshend does not simply find the key ready to be used. Instead it is held by Andrew DeSalvo, a man Henry met on his last visit to the Water Prison World. Andrew has fallen victim to Walter Sullivan's murdering streak and is now a ghost roaming the basement spiral walkway of the Water Prison. In order to obtain the key, Henry must first pin Andrew down using a Sword of Obedience.
As the lengthy name states, the key must be used to unlock the generator room in the Water Prison's B2 floor, allowing Henry and Eileen Galvin to exit the Water Prison world.