Lock of the Saved

Source Adventurer’s Armory

This sturdy lock may be of any quality; the cost of making it a channel focus is in addition to the normal lock cost. When activated, the lock’s Disable Device DC and the break DC for whatever it is locking (such as a door or chest) increase by 5; the lock gains +2 hardness and +4 hit points. The lock retains these bonuses for 24 hours or until it is forced open (including picking the lock).