Witch-king, Sky Scourge is a mythic Legendary Creature — Wraith Noble card from Tales of Middle-earth Commander (LTC), collector number 511. Current market price: $2.66 (foil $1.80), TCGplayer market prices via Scryfall.
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.)