Lady Loki, Agent of Chaos is a rare Legendary Creature — God Sorcerer Villain card from Marvel Super Heroes Commander (MSC), collector number 365. Current market price: $1.39, TCGplayer market prices via Scryfall.
Whenever you cast your first instant, sorcery, or Villain spell each turn, exile it, then exile cards from the top of your library until you exile a nonland card. Lady Loki deals damage to each opponent equal to the difference between that spell's mana value and that nonland card's mana value. You may cast that card without paying its mana cost.