Karn, Scion of Urza Hour of Devastation exile up to one other

exile up to one other target nonland permanent

{1}{R}: Dragons you control get +1/+0 until end of turn

−2: Look at the top four cards of your library

They also serve as a great way to store a sideboard or cards together

then sacrifice it unless you pay its upkeep cost for each age counter on it

Karn, Scion of Urza Hour of Devastation exile up to one other+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."