It's not exactly about "demon spawn" just the horrors of a child lost in their own mind, which can make such things seem demonic, it has some religious culture in it, but it's mostly based around Isaac being scared, feeling like he's the worst thing out there living, which is causing him to "play this game in his head" whether he lives or dies and about the horrors around him that are trying to harm him (flies, spiders and such.) I will say it is one of the better games I've played on Steam and am looking forward to the DLC for Rebirth.