Nightshade Assassin (C19) from Commander 2019, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Darren Tan
• Card Text:
  First strike
  When Nightshade Assassin enters the battlefield, you may reveal X black cards in your hand. If you do, target creature gets -X/-X until end of turn.
  Madness 1B (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)