As an additional cost to cast this spell, exile three creature cards from your graveyard.
You may cast Skaab Ruinator from your graveyard.
9/22/2011 Skaab Ruinator is on the stack when you pay its costs. It can’t be exiled to pay for itself.
9/22/2011 You must exile three creature cards from your graveyard no matter what zone you’re casting Skaab Ruinator from.