As Mirrodin Besieged enters the battlefield, 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.