Blightborn Hydra

As an additional cost to cast Blightborn Hydra,
exile X creature cards from your graveyard.
When Blightborn Hydra enters the battlefield,
put a number of +1/+1 counters on it equal to
the total power of creatures exiled with it.
When Blightborn Hydra dies, return all
creatures exiled with it to the battlefield tapped.