Hmmm..
The First Celestial vs Daemons world should work out nicely for that..
It's a endless dry wasteland inhabited by two constantly warring groups.
The Celestials, who have an enormous highly organized bureaucracy. They tend to the elements of fire and air. Their power levels are static, and they rarely change in physical appearance. Their Bureaucracy has literally thousands of departments, each with Celestials of slightly different physical appearance and ability.
The lowest ranking Celestials are the Department of Messaging and Utility. They look more or less like normal humans, dressed in robes and sandals. Their only real outstanding attribute is their insane travel speed.
Then you have other common ones, like the Department of Organized Defense (Who's members look like sword carrying winged humans), the Department of Aggressive Counterattacks (Usually females on horseback, with winged armor), the Department of Binding (Looking like child-like humans with a pair of wings), the Department of Executive Decisions (Which prance around in crowns and robes).
Their counterparts are the Daemons, who wander around in small groupings. Daemons prefer earth and water, and often shape-shift. Daemons, as a rule, rarely form big groups, preferring to splinter apart. However, powerful Daemons sometimes bring large groups together. These are usually referred to as Daemon Princes.
There are more kinds of demons than there are names for them. Daemonic power waxes and wanes over time. Even a weak daemon can grow strong over time.
Neither are really good or bad, they just have.. issues with each other. They probably won't even care if you show up, so long as you keep out of the way.
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather