Source: Explorer's Guide to Wildemount

Wondrous item, rare (requires attunement)

This black leather apron is perpetually covered by blood, even after being washed off. You gain the following benefits while wearing the apron:

• Once per turn when you roll damage for a melee attack with a weapon, you can reroll the weapon's damage dice. If you do so, you must use the second total.
• Your weapon attacks that deal slashing damage score a critical hit on a roll of 19 or 20 on the d20.