Interesting concept, I could see how this could be expanded on.
Currently, it starts out incredibly difficult and just simply gets easier. You continue to grow stronger, but your enemies don't. The enemies also don't have any sort of passive effects, so they're all just a random healthpool with 1 damage and 80% hit, waiting for you to give them their stats.
Some of the relics could also use some balancing. There's 3 that heal you, and in order from worst to best... 1 heal when exploring, 1 heal when dealing damage (lose it if you miss), 1 heal per battle turn. The once per battle turn is strictly better than the damage one, since it's 100% chance instead of relying on your hit chance, and then both of those are going to heal you more than the per exploration one. And then there's shield per turn, which is also better than the heal on hit or heal on explore.
Then there's the +2 damage relic. Once you get one of these, you just start every single battle ahead of your enemy.
I do like the decision making you have to do during battles though. There's no avoiding bad options, only minimizing them, and sometimes that means trading some value to make sure you don't get hurt too bad. I also like that combat isn't a good thing. It's strictly there to kill you, with exception to the boss being the objective of the game. It makes the game feel especially harsh, which some people (like me) enjoy. I always felt like games that "make things harder" by introducing more enemies, but those enemies reward you, kind of backhanded, like... Ah yes, punishing me with more rewards, thank you. So I'm glad that didn't happen here.