The Gengar (10 / 144) card can be found in the Skyridge set.
Recently sold 3 times and based on those sales is worth around £69.95.
Currently, there are 4 open listings for this card on ebay.
This card sells in the range of £45.41 to £94.49, making it highly volatile.
This Rare card was illustrated by Kyoko Umemoto.