Ulamog, the Defiler

When you cast this spell, target opponent exiles the top half of their library, rounded up.

Ward—Sacrifice two permanents.

Ulamog enters 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.