How to make a Demon

Depends on what kind of demon you're after.
If you just want a feral one, then pick smth and slap horns/claws/fangs/wings on it and boom. Demon
If you want biblic type demon, i suggest you research the topic. They're usually sentient evil creatures or just devils

There's really a ton of options here, its up to what you want. I made a few demons myself but they're called that way only because they possess items and give some superpowers to the owner.

ok