Invigorate is a common Instant card from Duel Decks: Garruk vs. Liliana (DDD), collector number 19. Current market price: $0.34, TCGplayer market prices via Scryfall.
If you control a Forest, rather than pay this spell's mana cost, you may have an opponent gain 3 life. Target creature gets +4/+4 until end of turn.