I think you shouldn't be discouraged by people whining about the AI art. Less time spent on art means more time spent on mechanics, which is a win in my book.
The intro could elaborate a little more on the pc's experience with the area. It could explain why the pc is only wearing pants, and why the pc has blue hair.
Packing a big surprise is a pretty meh card IMO. Only really meaningful alongside 0-cost cards or Stardust Connection. Outside of that it's equivalent to stunning everyone for a turn.
If the player has over 100 block, the font shrinks.
Could add a card that poisons multiple enemies. Maybe steal "Bouncing flask" from StS (Poison random target 3 times).
The dark debuff is really annoying, especially when the common encounter applies it every other turn. One idea I had is to change the dark debuff into "the next x cards you draw are hidden", and have the boss succubus apply 5-6 dark, and have the common demon girl apply 2-3. It would make the effect less punishing from non-bosses, and let card-drawing be a counterplay.
One solution to the issue with enemies' poison is to remove poison from enemies entirely. If you want enemy DoT, then they could be given a variant that isn't block-piercing, maybe named Acid or Fire. (Acid could 100% be a DoT that only damages block though).
I'm torn on the post-boss transformation. On the one hand, yay boobs, and it alleviates the common "lose for smut" problem, but on the other, it kinda removes the whole TF aspect from then on. I'm guessing there will be more transformations to be afflicted with in the future, though.
Maybe it's just personal preference, but I would like it if buying cards was a bit more like StS, with individual cards with individual prices, and knowing 100% what card you're getting before you spend the money (yeah, you get to choose, but the selection is random and shown after money is spent).
I think the gamble intent has issues. I once heard a story about Slay the Spire's development, saying that the game became much more strategic when they added the enemy intents. Yes, the gamble is just one hidden intent at a time, but still. I think it should either have the same limitation as StS's "unknown" intent (not attacking) or display a number that shows their damage IF they attack. It would also be very nice to get a clear idea of what they actually do after, but that would probably come down to vfx.
I haven't had any bad experiences with it yet, but I can see Card Steal being really harsh with the wrong rng/deck, since there is no way to prevent it and no way to get the card back (unless you have Infernal Recall and get lucky). I feel that it would make the most sense if it was a weak-ish enemy that steals a single card and returns it on death, or maybe deal x damage to prevent. Enemy moves that move cards around between deck, discard and hand could potentially be quite interesting though.
This is the second wall of text I post in this feed. I'm sorry, I can't help it.