In this realm, Angels are heavenly and serves their lord: God. Devils serve their own lord: satan...

But fallen beings (commonly known as fallen angels or fallen devils) are the ones in the middle.. their none of the others (either because they were rejected by their kind or not supposed to serve any lords).

They aren't commonly found in this realm because they are found on earth as a Ghost. The only time you would find a fallen angel or devil in this realm, would be if they were chosen to be the seven suns.

the seven suns are a group of seven people who are turned into demi-gods from both lords and have a duty to protect or deal with any other things from outside the realm. They are usually over 100 years old mentally but didn't have the same age physically.