The Trevenant EX (19 / 160) card can be found in the Primal Clash set.
Recently sold 5 times and based on those sales is worth around £2.20.
Currently, there are 16 open listings for this card on ebay.
This card sells in the range of £1.40 to £3.00, 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.