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 £43.06.
Currently, there is 1 open listing for this card on ebay.
This card sells in the range of £16.49 to £69.63, making it highly volatile.
This Uncommon card was illustrated by Nakaoka.