I always feel like it takes guts to go heavy black like that because things can go wrong in a hurry. You pulled it off masterfully. I had never heard that Black Sabbath song until now. Music is a great tool to set the mood for what you're drawing because it can "anchor" the feeling you are trying to express. That was a good tune, it reminded me of Pink Floyd. I'm a David Bowie man when I'm drawing outer space, but then again, everyone probably is.
Like in movies where the actors run around in darkness, but what you see is a black screen and what you feel is the old lady in the next seat's hand on your crouch...
I'm glad to have introduced you to it - it is slightly heavier and a bit younger than Bowie - but the theme is the same I guess.