Vaporeon is no Energy generator, but being able to transfer resources is pretty useful
It's great, but you need to run it in the right deck, not every deck can get cards into the graveyard and some want to save them for reanimation like Living Death or recursion like Eternal Witness
Here is the way it works: Discard Energy cards one at a time until you have paid the Retreat Cost (or maybe more)
Simply browse the cards above or search for specific Umbreon cards to see current market prices, price history, and graded card values
Then there are the Arena-specific formats which can have a somewhat sporadic availability, like Momir or Oko's Madness, both of which involve making random creatures by discarding lands
Aside from the excellent pedigree this set has, Magneton's design is perfect for the cosmos holo pattern, which is incredibly prominent on this card