demon world
all demons in this story originate from the demon world, a lot of them are living in the human world currently but they migrated there from here for whatever reason. the demon world is sort of like a different dimension and pretty anarchical. (its a lot inspired by the demon world in yu yu hakusho lol.)
for the last several thousand years there are 3 self proclaimed kings, (lysander, nero, jiya) all with different ideals, some demons followed these kings but some still stayed in anarchy. however since they have a bit of a following = more power for them, and they were already the strongest of demons.
currently, lysander is the only known standing king in the demon world. nero mysteriously disappeared within the last year (see: "lunar caldonia"), and jiya has fallen very ill, his children in internal strife over who becomes the king in his place.
among demons, like 70% of them are mindless chaotic monsters who only exist to fill primal desires. these are typically younger demons who spawned within the last few hundred years. the remaining 30% are demons who have gained back their sanity and intelligence. these demons are usually older, but not always. they are also extremely powerful.
there is ever simmering war between magic users and demons (lysander is leading this charge). not all demons have intentions of overtaking the human world, but the upper elites are generally in favor of it. demons outnumber all human world inhabitants 10 to 1. however, they have no centralized government, it's generally anarchy. there are the self proclaimed kings and nobles alike who congregate among the more sentient crowd, but it's not like they rule over the whole demonworld (and not that they would want to either, it goes against demon philosophy to have human-style society rules and regulations).
sentient demons are originally created from amalgamations of various mindless demons fighting each other and forming one being (like the abyss watchers from dark souls 3). it generally takes centuries for them to be "born". demons born in this manner are referred to as "amorphous demons". among sentient demons there are certain families or clans as well. usually these are very old in lineage dating back thousands of years. they create offspring by severing off a piece of their spirit and eventually it grows into a fully fledged demon, thus the family grows. there is somewhat of a sense of superiority among these families, they've amassed power and influence.
generally demons only care about being physically powerful, so the greater strength off their family's individual power, the better off and higher standing they usually have. pretty much all elites are from one of these blue blood families. notably, the demon king nero is an amorphous demon. because of that he is very popular with the crowd of other amorphous sentient demons.