When Maw of the Furnace enters the battlefield, each player exiles a card from their hand face down, then draws a card. Turn all cards exiled this way face up. If the total mana value of these cards is 10 or less, put that many +1/+1 counters on Maw of the Furnace. Otherwise, Maw of the Furnace deals damage to the owner of each of the cards equal to that cards mana value, then sacrifice Maw of the Furnace.