Emrakul, the Last Hope

Delve, Convoke, flying, Annihilator 2
When no players control any Shades, Demons, Spirits or Decomons, exile Emrakul, the Last Hope until another Shade, Demon, Spirit or Decomon enters the battlefield.
"We have decided. We need to somehow bring back Emrakul in a slightly weaker state to free the multiverse, but not destroy it."