I really like this concept! I think at the moment it suffers from not having too many options: I've gotten a hand of two hearts I can't afford or one monster I can't possibly beat, and battles (especially against bosses) basically seem random. The numbers are a bit unforgiving, too, so it's hard to tell whether I have a real chance against any given monster.
I hope you keep working on this! The idea has a ton of potential, and I think you could develop it into something really interesting that doesn't play the same way twice.