Pyromancer's Swath is a rare Enchantment card from Modern Masters (MMA), collector number 125. Current market price: $0.77 (foil $1.24), TCGplayer market prices via Scryfall.
If an instant or sorcery source you control would deal damage to a permanent or player, it deals that much damage plus 2 to that permanent or player instead. At the beginning of each end step, discard your hand.