Beowulf Armor

Armor (light or medium), legendary, requires attunement

This +2 armor is layered with metal scales, but doesn’t feel any heavier than its mundane counterpart. Once per day as a bonus action you can choose a single type of creature as your mortal enemy: aberrations, beasts, celestials, constructs, dragons, elementals, fey, fiends, giants, monstrosities, oozes, plants, or undead. Alternatively, you can select two races of humanoid (such as gnolls and orcs) as mortal enemies.

You gain a +3 bonus to all weapon attack and damage rolls against your mortal enemy. The selected creature remains your mortal enemy until dawn the next day, allowing you to choose a new mortal enemy.