The quality of this is kinda wild, it sounds very professional. It sounds very fun and exploratory. Honestly this is great, there's too many positive things to say about it. Not gonna lie, my favorite part is the guitar, I could imagine myself just jamming out to that part!
The only thing I will say is that I am not super sure how well this matches the theme. I could see this appearing in a Halloween type game especially with the occasional organs, but it sounds very bright, determined, and exploratory which I don't think really matches the tone so well. I also don't really specifically being a boss battle song. Once again, I wouldn't bat an eye if it was used as one, but it doesn't really have any sense of urgency or intensity that I would expect.
But still, this is absolutely amazing, really looking forward to your future submissions!