Ulamog, the Defiler (389)

When you cast this spell, target opponent exiles half their library, rounded up.Ward—Sacrifice two permanents.Ulamog, the Defiler enters the battlefield with a number of +1/+1 counters on it equal to the greatest mana value among cards in exile.Ulamog has annihilator X, where X is the number of +1/+1 counters on it.