The Mightyena ex (101 / 110) card can be found in the Holon Phantoms set.
Recently sold 6 times and based on those sales is worth around £16.50.
Currently, there are 8 open listings for this card on ebay.
This card sells in the range of £8.05 to £24.95, making it quite stable.
This Rare Holo Ex card was illustrated by Ryo Ueda.
The fact that it is a EX card makes it one of the more valuable cards.