Maro, the Thousand Child

+3: Until end of turn, target creature you control gets +3/-X where X is the number of cards in you hand.
0: Target creature you control becomes a 6/1 devil with trample and haste until end of turn. That creature must be blocked if able next combat.
-10: Target player sacrifices creatures equal to the number of creatures you control. Then does the same for cards in you hand.