Ancient Bronze Dragon is a mythic Creature — Elder Dragon card from Secret Lair Drop (SLD), collector number 2487. Current market price: $20.26 (foil $19.29), 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.