Witch-king, Sky Scourge (LTC) (511) / Borderless

Flying Whenever you attack with one or more Wraiths, exile the top X cards of your library, where X is their total power. You may play those cards this turn. 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.)