Ruinous Waterbending is a uncommon Sorcery — Lesson card from Avatar: The Last Airbender (TLA), collector number 118. Current market price: $0.23 (foil $0.30), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, you may waterbend {4}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.) All creatures get -2/-2 until end of turn. If this spell's additional cost was paid, whenever a creature dies this turn, you gain 1 life.