Super cute game! Love the idea, and the choice of taking the defeated foe as your own or strengthening your own guy.
I think I had an issue of losing the first battle and then immediately becoming softlocked? But I reset a couple times and managed to beat the game. I do think the battle system could use some work -- RPS is cool, but unless I'm missing anything, it's just kind of random chance which one to use? I thought that maybe certain enemies could only use certain types and you might have to judge what you think they can do, but it seems like all of them could do anything, so you might as well just keep clicking your monster's strongest stat and pray from the best, haha. At one point also, I had a monster I liked, and then I tried reviving a carcass, and then it gave me a monster I didn't want, but it seemed like I was stuck with it now, which was a little annoying.
Anyway! Critique aside, I love the concept, the art was super fun, and I think you could totally turn this into something super cool. Fantastic job!