The Trevenant EX (19 / 160) card can be found in the Primal Clash set.
Recently sold 4 times and based on those sales is worth around £2.75.
Currently, there are 6 open listings for this card on ebay.
This card sells in the range of £2.13 to £3.37, making it very stable.
This Rare Holo Ex card was illustrated by Eske Yoshinob.
The fact that it is a EX card makes it one of the more valuable cards.