All-Seeing Arbiter is a mythic Creature — Avatar card from Game Day Promos (GDY), collector number 3. Current market price: — (foil $3.97), TCGplayer market prices via Scryfall.
Flying Whenever this creature enters or attacks, draw two cards, then discard a card. Whenever you discard a card, target creature an opponent controls gets -X/-0 until your next turn, where X is the number of different mana values among cards in your graveyard.