Please bear this in mind if you're shattering the world (especially if you're randomizing the religions in the game) since you might just end up with nothing but unplayable factions all over the map.
Shattered and Random Worlds will not allow you to circumvent DLC restrictions that lock playable pagans behind the Old Gods DLC, Muslims behind Sword of Islam, and nomads behind Horse Lords, for example. Let's start by making like a god and creating a world. So instead of trying to cover the whole DLC in one shot, let's focus in on the one mechanic that is absolutely the most literally world-changing one in the whole package: the Shattered World rules.