Ancient Bronze Dragon is a mythic Creature — Elder Dragon card from Battle for Baldur's Gate Promos (PCLB), collector number 214s. Current market price: — (foil $44.71), TCGplayer market prices via Scryfall.
Flying Whenever this creature deals combat damage to a player, roll a d20. When you do, put X +1/+1 counters on each of up to two target creatures, where X is the result.