My idea is for a small nation/faction RP that takes place after the victory of an evil Dark Lord over a fantasy world. Players would RP as part of the ruling faction, conquered nations enslaved by/collaborating with the Dark Lord, rebel movements, etc. in a world that has been devastated by an apocalyptic war and is in the process of being remade in the Dark Lord's image. Nations would be shadows of their former selves, and even the most autonomous would be fearful client-states of a powerful evil.

The setting would be what I call "High Fantasy OOC/Low Fantasy IC", meaning the setting would have as many fantastic elements as we like, but there would be limited magic "on camera" in the IC, as both an aesthetic choice to keep magic... magical and mysterious, as well as to put a limit on IC power levels while allowing for maximum creativity and freedom OOCly.

Here are some tentative setting details:

The World of Geryon

It was a hundred years ago when Dagon IV, Emperor of Aldebaran, covetous of the lands he did not rule and fearing his own mortality, enacted some heinous rite with the help of five of his closest lieutenants. Across the lands of Geryon, the sun shone an angry, dull red for ten days, with no moon at night, only strange and sinister constellations. From the Red Night, which ruined crops and plunged the world into panicked chaos, the Emperor emerged as a god of immense power, whose armies swept over the other nations of Geryon. His lieutenants too had become something more than human, weilding powerful and dark magics, and in time became known as the Immortals.

Some nations bent the knee, others actively collaborated with the new god-emperor, most were enslaved and destroyed. Aldebaran, once a rich and fertile riverland, was turned into a spoiled waste filled with the ruins of once proud cities, now sinking into poisonous bogs and fens and haunted by monsters and demons.

Now Dagon IV is master of all, ruling with the aid of his five Immortals and the feared Aldebaran Legions. They enforce a strict caste system in the lands they control, spreading the Cult of Dagon, and demand tribute in the form of children, woman and blood-slaves from the nations they've subjugated. Human sacrifice is offered to the god-emperor night and day in his haunted capital of Kuranes, and the nights grow longer and darker as the world itself begins to sicken. 

Some, however, resist still. The Scarred King, once the might King of Varyon and now little more than a guerrilla captain, has continued to inflict defeats on the Legions for a century, and is a legendary figure of hope to the masses chafing under the yoke of Dagon thanks to his military brilliance and... incredible... longevity. 

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Ok so that's a hasty sketch of what I have in mind. Everything is open to revision and obviously much will be expanded. Let me know if you'd be interested in joining!