Archnemesis is a rare Enchantment — Aura card from Marvel Super Heroes Commander (MSC), collector number 391. Current market price: $1.83, TCGplayer market prices via Scryfall.
Enchant opponent Whenever you attack enchanted player, that player loses 2 life. You draw a card and gain 2 life. Whenever a player attacks you, you may attach this Aura to that player.