The Bronze key is an item that players can steal from H.A.M. Guards in the storerooms (lower level) of the H.A.M. Hideout. These keys open small chests to the south-west in the H.A.M. Store room, accessible after Death to the Dorgeshuun. Entering the rooms requries either picking the lock on the door while the guard is facing away or using a crack on the south sides of the room. If the guard sees the player picking the lock, they will attack.
After using the key to unlock the chest, the player receives a message in the chatbox saying: "Your bronze key breaks in the lock." and the key disappears from the inventory.
All of the H.A.M. keys (bronze, iron, steel and silver) can be obtained at the lowest level of the H.A.M. Dungeon by pickpocketing the H.A.M. guards. Rewards from the chests include: coins (small amount), 1-5 pieces of random jewellery (ranging from sapphire to diamond,) and/or cut gems (also ranging from sapphire to diamond.)
For an exhaustive list of all known sources for this item, see here
|10 December 2015
(update | poll)
The examine of this key has been updated from "You stole this key from a guard deep in the HAM cave." to "You stole this key from a HAM guard (Used to open a chest deep in the HAM cave)." so its purpose is better described.