Ulamog, the Realm Reaper

Ulamog, the Realm Reaper costs {1} less to cast
for each Eldrazi creature you control.
When you cast Ulamog, the Realm Reaper, exile
all colored non-creature permanents.
Indestructible, haste
Whenever Ulamog, the Realm Reaper attacks,
exile half of your opponent's creatures, rounding
up.