It's not necessary given your flat earth setup but the red-hot mantle equivalent could be interesting cosmologically. If some souls go to the underworld instead of heaven they may bring some of their light/heat down with them and so make the depths of the earth a place of unexpected light while making the cold, dark cave/dungeon layer between the depths and the surface a kind of graveyard in both directions (scavengers feasting on detritus from above and below). The Greeks also had a thing for regular and chthonic gods which might be applicable. <|endoftext|> >NO