Realm Apocalypse

In a world where one day, over 600 demons appeared and created barriers all over the world, separating it, creating different realms. Each realm has it's own timeline and theme but all realms are made to only speak English. It is believed that it is because of the demons for such language restriction. There are 9 realms: modern, medieval, ice age, stone age, desert, steampunk, celestial, and hell. One realm does not know about the existence of the other, and only angels, demons, and those who possess the demon articacts.