Kilnmouth Dragon is a rare Creature — Dragon card from Legions (LGN), collector number 104. Current market price: $1.00 (foil $27.24), TCGplayer market prices via Scryfall.
Amplify 3 (As this creature enters, put three +1/+1 counters on it for each Dragon card you reveal in your hand.) Flying {T}: This creature deals damage equal to the number of +1/+1 counters on it to any target.