: Okay, all the evidence is more in-favor of it being the demon. I just find it
: disappointing that you never even get to see the alien god you're trying
: to "bury under millions of tons of rock."
Considering that the alien god was so big, its impact with the Earth 65 million years ago caused massive extinctions worldwide, I don't think it's the kind of thing that you *could* see in-game. Unless maybe the entire floor of the bottom level was the surface of his body or something.
Also, I'm pretty sure that the "demon" and "alien god" are one and the same thing, and that the smokey thing that you kill down there is just another dream or manifestation like all the other monsters in the game.