Bane Baldric

Wondrous item, uncommon (requires attunement by a ranger; see text)

This ornate embroidered sash of leather and velvet stretches across the chest from shoulder to waist. As a bonus action, you can select one type of creature, such as beast, dragon, fiend, etc. and attune the weapon sheathed on the bane baldric (which can be any one-handed melee weapon) to deadly keenness against such creatures for 1 minute. You gain a +1 bonus on attack and damage rolls with the attuned weapon and it is treated as magical. If the weapon is already magical, this does not add to its existing bonus. If the weapon requires attunement, it and the bane baldric can be attuned together as if they were a single item, requiring only one attunement slot. When you hit a creature of the chosen type with the attuned weapon, the target takes an extra 1d8 damage if it’s below its hit point maximum. You can deal this extra damage only once per turn. A ranger or other creature can use a bane baldric without attuning it, but each use requires a bonus action and lasts only 1 round. The bane baldric can be used in this fashion a number of times equal to the user’s proficiency modifier (maximum 5 uses) before its powers fade until the next dawn.