Astralos, The Grand Lich

Skeleton, Zombie, and Specter creatures you control get +1/+1 and first strike
When this creature enters the battlefield from
the graveyard, it becomes a Zombie Wizard creature type and gains hexproof.
Undying (When this creature dies, if it had no
+1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)