Shanna, Purifying Blade is a mythic Legendary Creature — Human Warrior card from Dominaria United Promos (PDMU), collector number 218p. Current market price: $0.56 (foil $4.05), 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.