Really bad game with good ideas. Most card games are already unbalanced and in favor of people who pay for better cards, this one get this to another level with additional random attack generator and deck builder with two kinds of crystals as currency to pay for putting a card in your hand. It ends up being 1/2 pay to win and 1/2 have luck with getting good cards to choose from(having better deck[buying one] makes it easier to get good compilation) so you can spend both of your crystal pools and have luck in fight with unpredictable dice rolls.
But seeing that as a beginner I just got a few fights with enemies whose deck was mostly rare cards which eliminated half of my hand in first rounds, I'd say it is more pay to win.
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You can receive ALL cards without spending money, only for achieving new levels. Just fight, complete quests and it will be enough ;)