I’m not a very big fan of the commonly held perception of Demonic possession. Even ignoring the fact that it perpetuates the negative stereotypes and misconceptions about the Daemons, I simply don’t think it’s very well thought out. To begin with, the very premise of non-consensual Demonic possession infers that the Daemon wishes to make the subject do something against their will or to their harm, or needs the subject to accomplish something that would otherwise be impossible for the Daemon to do alone. I have serious qualms about both of these scenarios.
For starters, if a Daemon wished to force a person to do something, I think there would be much easier and more effective ways to get it done than to personally assume control of their body and then perform the task through them. Even acts of self-mutilation and sabotage can be more easily achieved through deception or deceit than direct possession. Magic, as well as nature(as Magic is a part of nature), will always take the path of least resistance, and I highly doubt the Daemons make a habit of going to extra effort for inferior results.
Secondly, seeing as how Daemons are ancients begins of immense power, there aren’t too many instances I can envision that human assistance would be warranted. And if such an occasion were to arise, there would be plenty of subjects willing to volunteer themselves. This completely removes the need for non-consensual possession.
Finally, I am not entirely convinced that total Demonic possession of random everyday people is even possible without dire repercussions. In my experience Daemonic energy is quite powerful, even just being in the same room. Being touched by that energy can be intense, sometimes even bordering on uncomfortable. Personally, I believe that the energy encountered during full Demonic possession would cause permanent damage to the nervous system, if not other vital organs as well. This may not be the case for mediums and other experienced occultists who have trained their ability to handle higher energy levels, but for the average person, I have serious doubts about whether full possession is even possible.