Sylvan Might is a common Instant card from Eternal Masters (EMA), collector number 188. Current market price: $0.25 (foil $0.10), 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.)