The Gengar (10 / 144) card can be found in the Skyridge set.
Recently sold 6 times and based on those sales is worth around £114.20.
Currently, there are 3 open listings for this card on ebay.
This card sells in the range of £79.30 to £149.10, making it highly volatile.
This Rare card was illustrated by Kyoko Umemoto.