Forgotten Key
Wondrous Item,
Uncommon
(cost 110 gp)
Crafting Components
A key whose lock has been melted down or otherwise destroyed
Most commonly made of bronze with a long stem and a blank circular bit, forgotten keys are frequently sold to those wanting to explore a cave or tunnel under the city of Shalehold seeking the storied ruins and the supposed wealth within.
Once per day, you can use the key to make a thieves' tools check has an action to try to open any lock. If the lock was last opened less than five years ago, the attempt automatically fails and the use is wasted. You gain a an expertise die to this check for every decade since the lock was last opened, to a maximum of 1d8.
When you use this item, roll a d20. On a result of 1, the key loses its magic and becomes a mundane item.
Source