The Dialga EX (99 / 101) card can be found in the Plasma Blast set.
Recently sold 15 times and based on those sales is worth around £25.00.
Currently, there are 8 open listings for this card on ebay.
This card sells in the range of £15.37 to £34.63, making it quite 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.