There are three types of cards:
-Prey cards: mostly common classes in RPG like warriors, rogues, wizards... there are also some Felaryan jobs, like Fairy Hunters... Prey cards can fight each other and against pred cards, but less effectively in latter case, except some special cases, like Fairy vs Fairy Hunter. There are cards of tiny folk too, which are immune to normal prey cards and giant-size pred cards. Only human-sized predator cards can defeat them.
-Predator cards: have big stat, but require player to "feed" your own prey cards to summon them. However, there are size-matter in feeding: you cannot feed prey cards that are too tiny to the preds, like feeding tomthumbs to giant naga. While the requirement are troublesome, pred cards can instant kill opponent's prey cards when attacking. Best way to deal with pred cards are using other pred cards and support cards
-Support cards: they do support stuffs, like protect a prey card from being eaten for a few turns, turning a giant-size pred to a human-size one so that human-size prey cards can deal with them.