Very unique art style, and very polished for a gamejam timeframe. Sound effects, animations, an inventory/deckbuilding system. Thank you for the fun experience!
I only ran into one bug and it didn't break anything. If you highlight two squares with the centipede, but those squares don't make a valid configuration, the centipede returns to your inventory as a centipede, rather than a card.
Overall excellent for a jam, not sure if you're planning to carry this game on, but some feedback in case you do. I didn't quite get the addicting sensation that I normally do from deckbuilders, although probably for a lot of reasons you're already aware of and just didn't have time to implement.
The biggest problem for me was that I had a hard time figuring out what my items were actually doing. To be fair, for the first few minutes I was clicking the button in the corner, which meant my character was facing the wrong direction. I started seeing effect icons after I started using the enter key. But still, I wasn't too sure if stun was doing anything, or what vulnerable did, or if bleeding was really working or not. Wasn't super clear if I was supposed to combo the hammer with the nails either, I saw the little pentagrams, and it just makes sense, but it didn't seem to do anything. I experimented a little with the eye, wondering if it really was just a dud, or if it could combo someway, but nothing seemed to happen there either.
Death should maybe be a little less punishing, or the first few encounters should be a little more randomized, I found myself not wanting to redo the first few encounters after dying. Maybe lose health or a life, rather than a hard restart? Or maybe it just needs balancing so death is less likely before you feel invested.
I'm 100% sure you would already plan to improve this for a full release, but I'll still mention it since it's something I noticed. It seemed like I got fixed cards every time, I didn't notice any randomness or rewards for performance. I thought maybe choosing the 25 health miniboss would give something cool, but I couldn't beat him.
Last thing, I can't call myself an expert on dark settings like this, but if you make a full game out of it, I'd recommend giving it a spot of light to contrast with the overall setting. (Like Clementine from Walking Dead, or the adorable little critter cards from Inscryption.)