Whetstone of Tudwal Tudglyd

When you spend 1 minute using this unremarkable-looking whetstone to sharpen a blade, if you are a fine warrior the next time you deal damage with that weapon, you deal an extra 7 (2d6) damage. If you are a coward however, for the next 24 hours you deal the minimum amount of damage with that weapon.

Source: Level Up Advanced 5e · OGL-1.0a · 5.1