Source: Baldur's Gate - Descent into Avernus

Weapon (battleaxe), legendary (requires attunement by an evil cleric or paladin)

Fane-Eater is a battleaxe belonging to Arkhan the Cruel (BG:DA, page 111).

You gain a +3 bonus to attack and damage rolls with Fane-Eater . If you attack a creature with this weapon and roll a 20 on the attack roll, the creature takes an extra 2d8 necrotic damage, and you regain a number of hit points equal to the necrotic damage taken.