Incremental Blight is a uncommon Sorcery card from Shadowmoor (SHM), collector number 70. Current market price: $0.40 (foil $7.63), TCGplayer market prices via Scryfall.
Put a -1/-1 counter on target creature, two -1/-1 counters on another target creature, and three -1/-1 counters on a third target creature.