Spawnsire of Ulamog

Annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent.)

[4]: Put two 0/1 colorless Eldrazi Spawn creature tokens onto the battlefield. They have "Sacrifice this creature: Add [1] to your mana pool."

[2]0: Cast any number of Eldrazi cards you own from outside the game without paying their mana costs.