Karn, Scion of Urza

+1: Reveal the top two cards of your library. An opponent chooses one of them. Put that card into your hand and exile the other with a silver counter on it.−1: Put a card you own with a silver counter on it from exile into your hand.−2: Create a 0/0 colorless Construct artifact creature token with "This token gets +1/+1 for each artifact you control."