Like most Pokmon cards, the value of Mega Dragonite ex depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Ascended Heroes)
The best thing about finding new interactions between cards is that sometimes an idea strikes you to just make a small change to a type of deck that is already out there
Here's a quick sidebyside you can scan before you buy: Which games use Japanese size card sleeves vs
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Pygmy Giant: This creature has an ability that allows you to exchange control of Pygmy Giant and target creature you control until end of turn
Jokulhaups is the only complete boardwipe in the deck, Wake of Destruction, Bend or Break, Thoughts of Ruin and Stone Rain give us a wide range of options to set the opponent back, or reset the game completely