Loved the artwork! I spotted a Hollow Knight reference near the boss as well if I'm not mistaken, which I'm sure was a big inspiration for this game judging be style and themes.
Interesting idea, lose parts of yourself to get stronger. I never completely got how it worked even after beating the game. It looked your lost parts were put in a ball, which you need to get back eventually but I most of the time I didn't where that ball was. There also seemed to be some sort of gamble mechanic by losing your parts, as in there's a negative to losing them and gaining all that strength, but besides the soul one which directly stated that if I stopped moving I would take damage I didn't fully get it either. It seems like some more feedback about all of these systems would have helped me understand them. Most of the time they felt invisible.
That being said, this looks like a tremendously huge undertaking for a game jam and I'm very impressed by the animations and all of the systems needed for the game to work in its current state. Well done! :)