if you build decks by color, it doesnt really matter when a card was released
That means you can play Atraxa in poison decks, +1/+1 counter decks, planeswalker decks and basically anything else that uses counters
Like most Pokmon cards, the value of Shiftry 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 (Crystal Guardians)
This card is most likely a 1-of or 2-of in any white control deck, even if it is playing a bunch of planeswalkers, just because it prevents you from getting screwed over from an unexpected angle
Board complexity is about understanding how that card interacts with all the other cards
The CardValueScanner card value scanner app for pokmon tcg