The idea is fantastic and the level of polish is stunning. There's so much content here for a 4 day jam, incredible work.
However, I feel like the game is too random. Especially with some pieces. There are so many options for them to move, that some cards moving them in random direction cannot be predicted at all - this could potentially mean a lucky win or losing a piece or a totally useless move. This is a way of making strong pieces (such as queens and rooks) less viable, but... I don't know.
The most unfair thing though is random enemy positions at the start. This could mean, that you could lose valuable pieces at the very beginning without an opportunity to do anything.
I like that you get a lot after each game (card, piece(s) and relics) - this makes game more varied quickly.
Inspirations to Bergman's movie is top notch, however I think that there are way too many similarities to Slay the Spire (at lease relics could be named something else, you know :D).
I had a lot of fun playing it, though I can imagine somebody not into chess might give up way earlier ;)