I would appreciate some assistance in learning about a particular topic.
If my interpretation is correct demons from The Bible and symbiotes from Marvel and vampires from Buffy/other IPs are all just different ways of talking about the same thing.
Could you please comment with or link to any relevant information you have on possession/symbiosis?
https://en.wikipedia.org/wiki/Demonology
In my experience demons are abundant. They have the ability to possess people when their mental faculties are down. For example, when people are on drugs or alcohol. You can actually guard against this if you are an alcohol user for example. They really don't like that.
Also, it looks like some people are far more easily possessed than others.
Angels likely have the ability to possess people as well. I haven't really seen that sort of thing personally.
Also, if you have been under general anesthesia.
A lot of people get possessed in hospitals.
It's as if certain substances leave the front door wide open so anyone can walk in and take up residence.