Gloom, Lord of the Undead

Unsettle (When this card leaves your graveyard, create a 2/2 black Zombie creature token.)
Hexproof, Indestructible
Whenever a creature enters the battlefield, if it entered from your graveyard or you cast it from your graveyard, you may return Gloom, Lord of the Undead from your graveyard to your hand.
"No grave deep enough."