Shanna, Purifying Blade is a mythic Legendary Creature — Human Warrior card from Dominaria United (DMU), collector number 317. Current market price: $0.33 (foil $0.35), TCGplayer market prices via Scryfall.
Lifelink At the beginning of your end step, you may pay {X}. If you do, draw X cards. X can't be greater than the amount of life you gained this turn.