Like most Pokmon cards, the value of Team Rocket's Mewtwo 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)
Just don't try to remove its mask, or you're in for a world of pain
If your opponents attempt to rebuild their armies you can hit them with another conditional board wipe, like Magmaquake, Molten Disaster or Breath of Darigaaz
Where the Arkhive finds the most value in terms of sheer size, however, the Superhive makes its mark thanks to its all-encompassing nature
You should try the game with prebuilt decks for a while, before setting out to build your own
Tron decks and the Eldrazi are also colorless