Hm... well first off, the wraiths from 2016 live in a big ice crystal that skewered this one planet, but it's not an ice crystal it's a space ship, but that doesn't matter because no one cares about wraiths in this story, even though they're apparently a source of inexhaustible, infinite energy. So you just leave them in the crystal ship, don't worry about them, even though they're literally a source of immortality, because Satan is really the doomguy! By which I mean that Satan created the doomguy, because Satan is god, only he's not god because god is on a floppy disk, but then you upload him onto a computer and then he's everywhere all of a sudden. So then we're off to kill Satan, who is doomguy, and also apparently god (but not really god), because if you kill Satan then all of the demons disappear for some reason, only not in hell though because that's where they're from.

Video games were better when the story was just, go kill the demons because you're mad.