This is another setting I've come up with and ran to completion, largely centered around concepts such as dualist religion, cosmic light & darkness and a world that's gone through great catastrophe in the past. It's a land where iron is sourced via falling stars and those with money have their equipment made from bronze (those without have to tolerate equipment of copper, chitin and stone.)
For the first campaign I ran in this setting (creatively dubbed Desertgame), The party consisted of an enforcer/former slave driver, an ape-man from tropical islands who had a dedicated mage-killing spear, a homeless man turned brawler, a capricious sorcerer and a crab-humanoid monstrosity. The homeless brawler was rocked by a simple arena pit fight and the player wanted to change characters, so he ended up sold into slavery after the rest of the party ditched him and was replaced by a moralizing wandering healer (who had his arm cut off later on.) The crabboid was a menace to the party and everyone around him until he attempted to challenge an automaton guardian of an ancient arcology and ended up as a burning smear on the wall. That player then joined as a warty axe warrior from a far away eastern island.
The gist of that campaign was that an extremist heterodoxy from the north had ventured down into Jeddham in search of a means to recreate the god that left them and their land without sunlight or warmth. They had stumbled upon a great and ancient machine from a lost civilization which worked with geometry and mathemetics to alter reality to the whims of the user. What they didn't know is that by its flawed design, anything created through this machine would invariably lead to ruin and misery. The party fought their way through a pyramid necropolis full of cult knights, skeletons, mummies and shadows of souls dredged up to serve the new god-being to be. It ended with them managing to destroy the machine and prevent the fetal god from manifesting fully in reality, putting a stop to the threat before looting the fortune the splinter sect had brought with them and living the high life. Well, high life for those who weren't killed at least.