I'm playing RavenQuest like a madman...
There's a specific limited set of cards—2 cards for every ability, and you can only choose one of the two. So in this case, I'm using the bypass partial shields, increase base damage on my Frostbolt ability. The other choice is increase base crit for that ability by 10%.
So they add some flavor to the ability... but the game gives you lots and lots of (unminted) cards, so after like a week of playing I have just about every one. The cards are better with higher rarity, no doubt, but since the game doesn't let you mint cards, there's no real need for the secondary market—the ones on TT are all minted NFT cards from "special" packs that you buy on the website, which contain the same cards you can earn in-game, with the additional aspect that they can be sold because they are NFTs. Going out on a limb here, I'd say 99% of players ignore the fact that cards exist as NFTs, since you can't earn 'em in-game.
Game is fun, though. I'm getting waaaaaaay behind on my GU battlepass because of it—to the point I'm nearly unable to complete it in time to reclaim my spent GODS.