The Dark Gyarados (36 / 109) card can be found in the Team Rocket Returns set.
Recently sold 3 times and based on those sales is worth around £40.83.
Currently, there are 2 open listings for this card on ebay.
This card sells in the range of £21.13 to £60.53, making it quite volatile.
This Uncommon card was illustrated by Nakaoka.