I could see a chapter on "cosmic conflict and your campaign world." Something like: 1) Cosmic Conflict Largely Happened Millennia Ago (example Nethir Vale and Greek mythology), 2) Cosmic Conflict sporadically touches the mortal world (example Eberron), 3) Cosmic Conflict is ongoing (example the Blood War), 4) End Times Cosmic Conflict is Coming (example Norse mythology), and 5) Cosmic Conflict Ended Recently and World Sucks (example Dark Sun). [There probably isn't much need for Cosmic Conflict Ended Recently and World has Never Been Better.] There are some subtle (and not so subtle) differences in how you would play hostile outsiders based on those scenarios: the fiend who is hiding from the Forces of [Good/Law/whatever] and only causing trouble if it can't get caught vs. the fiend who thinks its time is now and has no problem running around causing trouble.....