Devils Dance

I've had this piece not finished for a while and I wanted to finish it. The piece starts calm and slow, then suddenly becomes very chaotic and the piece starts sounding off and wrong. It has a melody that goes throughout the piece, but gets distorted and changed. The chords become very odd sounding and start to make it sound polytonal to the melody. Then it ends abruptly with lots of tension in the final "chord" and doesn't feel like it truly ends.