technically every devil is man-made since devils are the physical manifestation of human fear.
Though, all the devils we have seen thus far are devils made from the fears of things that have (or had) already existed like gun, katana, war, etc.
But, what if there are fears of things that have NEVER existed? Fears that humans created themselves?
What if, for example, I tricked my friends into thinking that "AYO THE SCARY HALF-MAN HALF-PIG DEMON IS GONNA COME EAT YOU TONIGHT" and made them afraid of the "half-man half-pig demon"? The fear of that thing would be created and thus the devil representing the demon would also be created. It will be weak, sure, but I can just trick more people and keep making up messed up stories about the creature to make more people afraid of it and thus strengthen the devil.
With my theory, literally, any devil could exist. Even the ghost devil exists although we haven't seen any ghosts"in CSM yet. And if my theory were to be true, people would abuse the shit out of it.
Now, imagine that someone, or rather, some groups of powerful people that can easily control people, decided to use their power to inject fear into people in order to manufacture a devil that will benefit them.
For example, the Japanese government could have kidnapped a bunch of people from all around the world, torture them and find a way to tell them that 'The devil that is royal to Japan and is able to destroy any country in the world' is behind their torment. With this, the fear of 'the devil that is royal to Japan and is able to destroy any country in the world' is created. And thus, the powerful devil that will work for Japan is created.
How do you make the devil stronger? Make humans fear more and more. Capture more humans, more torture, more brainwashing, more fear.
Here's the fucked up part:
Who are the most gullible, easy to be kidnapped, easy to be brainwashed, and easy to be scared? Chi