Hey, wow, this sounds very complete as a full music track, going above and beyond the call for just a leitmotif! One thing I found interesting about this piece is that, to me, it seems to be mixed in a way that is very reminiscent of classic JRPG soundtracks, albeit with some twists here and there. I could see this being a song during battle gameplay!
It definitely gives off an epic feeling, but I think the most interesting part for me is the wild stuff going on with the piano part. As it builds, something about it was oddly funny to me — but in a good way! I was picturing in my mind someone physically playing that part on a piano, and the way I imagined it, this hypothetical piano player was slowly panicking trying to hit the keys on the right beats and just barely hanging on, and then at the end just starts desperately slamming out those chords. It may have had something to do with the note velocity or the scales you were using. However, the unexpectedness of it definitely did develop the tension and added some "character" to the villain! Really cool *whoosh* outro effect at the end, too! Nice job!
Also, tangentially related anecdote: I listened to your piece a few times and was taken aback by a strange sound at the very end. "Hmm, that's an odd way to end it," I thought. Then I listened to it again, and didn't hear the sound, but then I leaned back in my chair and... *squeak*... there it was! Yes, somehow I had managed to consistently make my chair squeak at the exact same point in your song like three times in a row and I thought it was part of it. Ha, maybe that's an idea for your next song... the "Chair Squeak Symphony"! That will really throw people off! 😄