Thunderstaff is a uncommon Artifact card from Darksteel (DST), collector number 153. Current market price: $0.31 (foil $1.12), TCGplayer market prices via Scryfall.
As long as this artifact is untapped, if a creature would deal combat damage to you, prevent 1 of that damage. {2}, {T}: Attacking creatures get +1/+0 until end of turn.