Belltoll Dragon is a uncommon Creature — Dragon card from Dragons of Tarkir (DTK), collector number 46. Current market price: $0.21 (foil $0.41), TCGplayer market prices via Scryfall.
Flying, hexproof Megamorph {5}{U}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.) When this creature is turned face up, put a +1/+1 counter on each other Dragon creature you control.