Nightshade Seer is a uncommon Creature — Human Wizard card from Urza's Destiny (UDS), collector number 63. Current market price: $0.17 (foil $4.19), TCGplayer market prices via Scryfall.
{2}{B}, {T}: Reveal any number of black cards in your hand. Target creature gets -X/-X until end of turn, where X is the number of cards revealed this way.