Coat of the Duelist (5e Equipment)
From D&D Wiki
Armor (leather), legendary (requires attunement)
This leather armor darkened by age is garnished with a flowing cape, patrician, with a flowing golden coiling pattern that seems to shift in bright light and emanates a soft sheen in darkness. This cape, whilst elegant in design is outdated in design, demonstrating the antique styling and nature.
Furthermore, when you hit with an opportunity attack, you may also move up to your movement speed as part of an opportunity attack.
However, when attuned to this item your very essence is filled with a sense of nobility and purpose, and you are considered Cursed:
Curse. Whenever you cast a spell, use a magical item, make an attack roll, or use an effect that targets a creature, that creature becomes your main focus for 24 hours or until that target dies. While you have a main focus, you have disadvantage on attack rolls and spell attack rolls against any other creature besides your target, and must make a DC 18 Wisdom saving throw to attempt to target any other creature besides them.
Furthermore, if someone else tries to intervene and target your main focus with a spell, attack, or effect or if you move away from your main focus, you are overcome by the cowardly nature of your actions and take 3d8 psychic damage as your feel the honor of the past wearers rages through your mind.