Gates of Eternity
This world is a field of a battle that is older than time, that exists in its current form as form of a compromise between beings that escape human comprehension. Beings that permanently try to recreate reality itself to suit their needs, forever unhappy and unsatisfied with the current state of affairs.
Even world itself seems to be tired with the mortals, permanently trying to get rid off them. Magic, the only weapon against madness of the reality, tends to create more problems than it fixes. Civilizations create their cities on the graveyards of their precedessors, always wondering how long will they manage to exist before they will join them in their eternal slumber.
Countries, rather than cooperate against their common threats, play games that mirror those played in Heavens. Always fighting for more territory, more influence and more power, with multitude of schemes, sects, demons and worse beings always trying to undermine their position.
Woe to the mortals when Gods march to war.