The Hydreigon EX (103 / 108) card can be found in the Roaring Skies set.
Recently sold 7 times and based on those sales is worth around £7.90.
Currently, there are 7 open listings for this card on ebay.
This card sells in the range of £4.67 to £11.13, making it stable.
This Rare Ultra card was illustrated by Ryo Ueda.
The fact that it is a EX card makes it one of the more valuable cards.