The logic behind Black Heaven

I thought I was reading on Max's blog, and I could be wrong about where my source of information is coming from or if I actually read it, that Suu keeps coming back because he's now bound the the black mage so his body is simply a vessel of power and you simply defeat it and eventually the power returns or something like that. It doesn't explain the first stage but it could be just the soul of a boss lingering in an area or something.