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 also one of the fifty required items to hand the dwarf in the Mournings End Part II quest if you need a death talisman.
The jail key is not required for exiting the cells.
This key cannot be placed upon the key ring.
For an exhaustive list of all known sources for this item, see here
- While most items are left on the ground for 2 minutes after the death of a monster, the jail key only stays on the ground for 1 minute after the death of the Jailer.