Also in response to the new upgrading card art. One app for apple is Immortalis and when cards upgrade to certain levels they mirror the cards and alternate the colors. that wold be cheap and easy.
Card ideas: Retaliate, whenever card is attacked it attacks in response. Reach, can block creatures with flying. would be cool to see a possible expansion in campaign such as India or viking related. More mythical creatures would be cool such as, a phoenix, skeletons or even dragons. I know some of this maybe frivolous, but it would be cool.
Honestly, it would be nice too see more than 3 cards in a singular pack. Moreover, as you level up increased pvp stamina and campaign stamina. It honestly seems too short for later levels. That's all i got to say.
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Awesome ideas. And definitely more mythical creatures coming!