The Keldeo EX (142 / 149) card can be found in the Boundaries Crossed set.
Recently sold 3 times and based on those sales is worth around £22.41.
Currently, there are 3 open listings for this card on ebay.
This card sells in the range of £19.62 to £25.20, making it stable.
This Rare Ultra card was illustrated by 5ban Graphics.
The fact that it is a EX card makes it one of the more valuable cards.