Source: The Book of Many Things

Wondrous Item, legendary (requires attunement by a Bard, Sorcerer, or Warlock)

This colorful, harlequin domino mask is edged with pearls. While wearing this mask, you gain the following benefits:

Charismatic Focus. You can use the mask as a spellcasting focus. You gain a +3 bonus to any spell attack rolls and spell saving throw DCs that use Charisma as the spellcasting ability.

Marvelous Escape. When a creature hits you with an attack roll, you can use your reaction to disappear in a puff of smoke and colorful sparkles. You take no damage and instead teleport, along with anything you are wearing or carrying, to an unoccupied space you can see within 30 feet of yourself. Once this reaction is used, it can’t be used again until the next dawn.

Topsy-Turvy. When you roll a 1 on a d20, you can treat the roll as if you rolled a 20 instead. Once this property is used, it can’t be used again until the next dawn.