Mirri, Weatherlight Duelist is a mythic Legendary Creature — Cat Warrior card from Special Guests (SPG), collector number 15. Current market price: $8.90 (foil $12.64), TCGplayer market prices via Scryfall.
First strike Whenever Mirri attacks, each opponent can't block with more than one creature this combat. As long as Mirri is tapped, no more than one creature can attack you each combat.