The Dark Charizard (21 / 82) card can be found in the Team Rocket Unlimited set.
Recently sold 13 times and based on those sales is worth around £26.00.
Currently, there are 16 open listings for this card on ebay.
This card sells in the range of £17.51 to £34.49, making it quite stable.
This Rare card was illustrated by Ken Sugimori.