A completely imaginary world: Seven Domains
The Seven Realms are composed of seven races:
Gods, elves, demons, humans, vampires, ghosts, demons
Demons are a small group created by the crossbreeding between the other six major races. They are rare in number, but have power second only to the gods...
Perhaps, it's not how strong the group itself is. Rather, if you are not strong enough, you simply cannot survive in this world where the jungle is strong and the strong eat the strong...