Magnemite into Magneton builds the energy engine that fuels both Magnezone ex and Miraidon ex
Umbreon has a great first attack, Moonlight Fang, which makes it invulnerable to any Pokmon with Pok-Powers or Pok-Bodies The main problem I soon found was that Umbreon is too easy to play around by Power/Body based decks
As such, if you have Castle Locthwain in your collection, you should play it, but if you don't, I'd make this the lowest-priority card in the deck to spend your wildcards on (although it is worth adding to your collection if you are interested in Explorer or Historic because a lot of decks play it)
In this case, though, it was not the slow and painful torture of Nephalia Drownyard that ended the opponents life
But which one should you choose for your cards
Still, MTG players are a wily lot and the most insane skilled players will find a way to make this pop off.