Post-Apocalyptic Earth
The world after the nanocloud outbreak - an unintended release of nanomachines that resulted in an uncontrollable reconfiguration of genetics in people. Most deaths were due to schisms that took place after societies collapsed around the world, the reasons yet unknown. The survivors are almost universally merged with individually-controlled nanocloud formations, in a symbiotic relationship where each host's nanocloud works for that host, creating powerful beings with huge potential.