>>518541673
Demonic possession is extremely subtle. The possessed person is likely unaware of what is happening to them for most of the experience. It can start with something as innocuous or trivial as indulging in porn or getting drunk. This is the Invitation stage. The host will enjoy the activity and repeatedly go back to it, this is Infection.

The demon will "reward" bad behavior with skills and knowledge that the host doesn't have. This will in turn make them more powerful and successful. This reinforces in the host's mind that he is doing something "good," so he goes deeper into depravity. We call this demonic Obsession.

If the host starts to become aware of this and tries to change his behavior, the demon will start causing them pain and discomfort. Eventually this is pushed to a point where the host functionally ceases to exist as an individual. This is the Domination phase. At this point, the person is completely helpless and requires outside intervention to break the binding.

Invitation > Infection > Obsession > Domination

There is a physical, material aspect to it as well, but that is not understood. It's likely that the precise mechanism is not something that is knowable, presenting an epistemological problem.

There are people who deliberately invite these entities into their person. In the US it is mostly older families, pilgrim era type people. This is inherited and passed down deliberately. A demon can be passed to an infant. Why would someone do something so incredibly fucked up? Because they're evil.