Might of Old Krosa is a uncommon Instant card from Time Spiral Remastered (TSR), collector number 217. Current market price: $0.35 (foil $0.36), TCGplayer market prices via Scryfall.
Target creature gets +2/+2 until end of turn. If you cast this spell during your main phase, that creature gets +4/+4 until end of turn instead.