Here's a random idea I had for Pathfinder campaign using LJPDesigns's Neo-Exodus as the base setting. Among other things inspiring this are 80s cartoons like Jayce and the Wheeled Warriors, Spiral Zone and Thundercats as well as maybe the Pirates of Dark Water. I will be making some changes from baseline Neo-Exodus and adding in at least one template from Obsidian Apocalypse.
About 100 years or more ago there was a meteor shower that rained down day and night for about a month solid. Riding in those meteors was a great and terrible force for evil as a Star Spawn of Cthulhu was transferred to the surface of Neo-Exodus. Aided by the aboleth and renegade members of the First Ones a great and terrible ritual was enacted that completed removed all cavians, p'tan and enura from the planet and erased the memory of them ever existing but instead giving rise to a new race of beings known simply as the kymera.
Quickly consolidating its power the star spawn took over as the new sovereign and god of the First Ones. It then set about creating and implementing eldritch machines capable of blotting out the sun from sentient beings while leaving the land untouched and creating areas where the wills and minds of all sentient beings are reduced to little more than mindless slaves under the complete control of the First Ones. These Shadow Zone Projectors as they came to be called have been spreading out all across the globe in a bid for power and control.
But as one might imagine there are those among the nations of Neo-Exodus that would see this stopped. The projectors can be destroyed and with this destruction people return to normal. In some regions there are even mercenary groups of adventurers that specialize in seeking out and destroying the projectors as well as hunting down the ones responsible. These groups are often referred to as Raiders of the Shadow Zone.