Well, first of all, thank you for all the feedback, and for playing in general!
I'll go over some of your comments.
-Difficulty: It is a bit hard for me to balance the randomness of enemies, the power of the meta-progression elements, and the power of the different classes with the player skill. The first 20 difficulties could be very easy for veteran card game players while difficulty 0 could be nightmarish for new players. I'm thinking of ways to balance this, but the AI being kinda of weak right now is a result of me nerfing it so much for the sake of inexperienced players feeling cheated by cheap AI cards. Also, I'm thinking about nerfing the meta-progression skills since they are a bit too strong at the moment. Lastly, you mention enemies not playing differently. They indeed don't change much in the way they play, but rather their decks get stronger the higher the difficulty. I know this isn't ideal but it is what I could manage for now. Not playing cards only occurs because their randomly generated deck was maybe terrible and they didn't get any cheap playable cards.
-Strength and potions: This is true, strength goes from being quite desirable to being basically useless with meta progression. I'm thinking of ways to deal with this.
-Infinite loops: The game has a hard cap of 50(I think?) triggers per card per turn, but that does take some time to reach with two cards. People like going infinite so I left the cap very high, but it might be a bit much, I'll do something about it.
-Quests, meta progression, and how they are unclear: These two systems are in fact a bit unclear when you first pick them up. Hopefully, once I get tutorials going this issue will be solved. Also right-clicking to level-down should be implemented at some point.
-Keeping decks: A system to keep records of your previous run's decks is being worked on for both the purpose of just checking your best decks of all time, to having them available for custom runs once those get implemented.
-Cards rising bug: That was supposed to be fixed but a recent change might have broken them I'll check it out.
-Quest tracker: This was requested by other players and I do want to implement something like this at some point, so yeah, it is on the list.
-Giving enemies a face: This is indeed something I should do, I'm going to try and figure out a way to get this going at some point.
-Bugs: I'm really sad to hear you encountered so many bugs. Having a screenshot of what the field looked like when those occurred would've been extremely helpful for the bugs in combat. For the loading bug, I haven't encountered them myself lately, but they have been known to happen before. If you even encounter them again in the future, sending your savefile my way would be really helpful. It gets overwritten as soon as you start a new game, so if you intend to send it, please keep that in mind.
-Game crash: Haven't seen this one before. I'll try to test out the scenario you mentioned.
-Card combinations being bad: That specific scenario (Add 1 mana for a cost of 2) was supposed to be forcibly fixed already but I guess it can still happen, I'll look into it. In general, I do want to keep some level of silliness for card generation, but I'll think about restricting more dumb combinations in the future.
-The Assassin quest; To unlock the assassin you need to craft a Minion with 1 active and 3 passives, add it to your deck, and play it during battle for the achievement to unlock.
Again thank you very much for your feedback and comments friend!