The Black Beast

Flying, Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.)
As long as The Black Beast is paired with another creature, each of those creatures has 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.)