Nightshade Assassin is a uncommon Creature — Human Assassin card from Commander 2019 (C19), collector number 123. Current market price: $0.36, TCGplayer market prices via Scryfall.
First strike When this creature enters, you may reveal X black cards in your hand. If you do, target creature gets -X/-X until end of turn. Madness {1}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)