Sylvan Might is a common Instant card from Duel Decks: Mind vs. Might (DDS), collector number 51. Current market price: $0.05, 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.)