Sewer Nemesis [Commander 2011]

Set: Commander 2011 Type: Creature — Horror Rarity: Rare Cost: {3}{B} As Sewer Nemesis enters the battlefield, choose a player.Sewer Nemesis's power and toughness are each equal to the number of cards in the chosen player's graveyard.Whenever the chosen player casts a spell, that player mills a card.