Ulamog, the Ceaseless Hunger

Ulamog, the Ceaseless Hunger

Legendary Creature - Eldrazi | Power/Toughness: 10 / 10 (CMC 10)
When you cast this spell, exile two target permanents.
Indestructible
Whenever Ulamog, the Ceaseless Hunger attacks, defending player exiles the top twenty cards of their library.