Induce Despair is a common Instant card from Duel Decks: Zendikar vs. Eldrazi (DDP), collector number 53. Current market price: $0.11, TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, reveal a creature card from your hand. Target creature gets -X/-X until end of turn, where X is the revealed card's mana value.