Mirrodin Besieged is a rare Enchantment card from The List (PLST), collector number MH1-57. Current market price: $5.37, TCGplayer market prices via Scryfall.
As this enchantment enters, choose Mirran or Phyrexian. • Mirran — Whenever you cast an artifact spell, create a 1/1 colorless Myr artifact creature token. • Phyrexian — At the beginning of your end step, draw a card, then discard a card. Then if there are fifteen or more artifact cards in your graveyard, target opponent loses the game.