No idea if this is a spoiler or not but I don't get to use it much. Spoiler It's hard to know what is real and what isn't in the prologue. The fire demon is trying to take Snake back to hell from where he escaped, I presume. It also raises some interesting points about the bosses he fights in MGS. Is Psycho Mantis even real? Is he still suffering from long term mental health issues? A piece of metal sticking out of his head can't have helped much.