The Gengar (10 / 144) card can be found in the Skyridge set.
Recently sold 3 times and based on those sales is worth around £102.98.
Currently, there are 4 open listings for this card on ebay.
This card sells in the range of £92.09 to £113.87, making it quite volatile.
This Rare card was illustrated by Kyoko Umemoto.