I will keep it short. What’s a patron demon and how you find it? Also what’s the relationship between you and him/her is supposed to be like. I tried to find the information through the search function, but it was futile. The closest thing that I got is this Patron Demon spirit.
Please keep in mind that i am oversimplifying things here but basically a patron demon would be a demon one worships and/or is particularly close to. It comes from demonaltry and follows the same thought process as a patron god. They are basically a go to spirit for the individual.
As to how to find them, it comes down to reading about various demons, finding one that seems appealing or draws your eye, and getting to know them by working with the spirit themselves to see if you jive well with them.
Thanks for the informations!