Put X +1/+1 counters on it, where X is the number of growth counters on Paradox Zone
There are a few factors that go into determining the value of your cards

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This shouldnt be the only method you ever use, youll want to give the cards a good shuffling in between using this method
Now, however, were getting a handy new Genesect ex to take its place, and this one is going to be very effective in metal decks like Archaludon ex
It's a long process though--you must battle various Club members first in order to battle the 8 Club Masters, and defeating a Club Master will earn you a Master Medal