Headbanging-worthy music! xD
The music reminds me of boss-battle soundtracks in JRPGs: They are familiar yet unique in their own right. But you managed to capture the good essence of this kind of music very well!
Like the other comments, the execution of bells is handled nicely: You managed to use the instrument that might be annoying if overused, to blend with the music and reflect the apprehension of the boss.
Nice job!