Ulamog, the pay to win

When you cast this spell, all opponents exiles the top
half of their library, rounded up.
Ward—Sacrifice X permanents, where X is the
number of +2/+2 counters on it.
Ulamog, the pay to win enters the battlefield with a number of +2/+2 counters on it equal to the
greatest mana value among cards in exile from
all players added up.
Ulamog has annihilator X, where X is the number
of +2/+2 counters on it.