Mirrodin Besieged

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.