A key for a chest.
This key can be used to open any steel, mithril, adamantite or meteorite chest.
The key can open any locked Treasure Chest. Right-click on the key, then left click on the chest.
This item can be bought from the Item Shop, though other players can sell it for game-gold after getting it from the shop.
Because of the cost, most people usualy use them for opening only the highest quality chests.