Luo Trebbel, Tinker Smasher

Haste
{3}{t}, Exile an artifact: Deal damage to target
creature equal to the exiled artifact mana value.
If excess damage is dealt this way exile the top
card of your library, you may play that card this
turn.
Stop.Holding.Back—{3}{r/g}{r/g}{r/g}, Sacrifice:
Deal damage to any target equal to double the
number of cards you own in exile.