Sylvan Might is a common Instant card from Double Masters (2XM), collector number 181. Current market price: $0.26 (foil $0.12), TCGplayer market prices via Scryfall.
Target creature gets +2/+2 and gains trample until end of turn. Flashback {2}{G}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)