transcendantviewer
Maestro of Meh
Take your time to think about it. But I'm thinking the mask giving her Expertise in Stealth and the ability to sneak attack with her unarmed strikes, as well as a number of sneak attack d6s equal to her proficiency bonus (or 6d6 in her case). I'm thinking it'll likely be her only magic item, so it could stand to reason that giving it a few spell abilities and making it Legendary Rarity could be doable.