Groundswell is a common Instant card from Duel Decks: Zendikar vs. Eldrazi (DDP), collector number 15. Current market price: $0.34, TCGplayer market prices via Scryfall.
Target creature gets +2/+2 until end of turn. Landfall — If you had a land enter the battlefield under your control this turn, that creature gets +4/+4 until end of turn instead.