The jail key is dropped by the jailer, found in the Black Knights' Base, deep within Taverley Dungeon. The key gives access to the jail cell containing Velrak the explorer, who will in turn give players the Dusty key which may be used to travel deeper into the dungeon. It can also be used to unlock the door that holds two dwarves, opposite to Velrak the explorer's cell.
The jail key is not required for exiting the cells.
This key cannot be added to the key ring.
For an exhaustive list of all known sources for this item, see here
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!