Ostarion, the Wraith King

{g}{b}{b}, Sacrifice a non-token wraith creature: King Ostarion returns to the battlefield from the graveyard tapped.

When King Ostarion enters the battlefield, create
X 1/1 black skeleton wraith tokens with lifelink and
exile X random creatures from any graveyard,
where X is the number of creatures in any
graveyard, up to 8.