Despite my Atheism, I do acknowledge the presence and existence of things...other than human. I don't like using the term supernatural, but for lack of a better term, or rather for lack of a shorter title other than "entities in relative co-existence with humans who are of similar if not greater or lesser in degree of consciousness in this plane of existence", it's the term I tend to use. As my long description explained, I do believe that these "creatures", these "entities" are merely beings that are indeed there, whose angers and joys can be triggered just as well as those of humans. 
I think of it this way: the world we live in now is like Lord of the Rings.
We are humans who live in the world with elves, dwarves, goblins, orcs, ghosts, demons, and all sorts of "inhumanity" that may exist indeed. What I do not label them as is the title of "mystical" or "magical" or "ethereal" because that is one thing I cannot hope to even believe: the ability to bend reality (albeit this sounds really cool).
Instead, I believe that they exist in separate consciousnesses from ours, either higher or lesser or even perhaps on-par with ours, depending on their influence on us. I believe that minds, not just human minds, but even that of "non-humans" are so great to the point that they can transcend their own inabilities and manifest beyond the constraints of their relative existences. Ghosts, for example, are entities who I believe are not the disembodied souls of a deceased human, but rather the consciousness of a human or other being that has gone beyond its initial form due to the happenstance of death. With its physical vessel is stripped of a means to survive, the consciousness is forced to transcend the physical and exist in a state beyond that.

I recall an old idea I had coined before on the existence of bodily possessions from outside sources that relates to this topic.

The concept of ghostly and demonic possessions. Here's how I view it: the reason why ghostly possessions are relatively more "comfortable" and less violent than demonic possessions is because ghosts, the post-mortem manifestations of humans, have before already experienced being in a physical body. Same goes for the body the ghost happens to possess at the time. There is little struggle because the body is used to the feeling of having a consciousness in it. Of course, it only turns violent when the ghost possessing it forces its way in and the person to be possess fights against this "forced eviction". Now demonic possession, however, is more violent because human bodies are not used to a non-human consciousness being inside it. This is why humans feel extreme discomfort because, for lack of a better (and less innuendo-goading) term for it, it doesn't fit.

Think of the human body as a porcelain container of hot water.

Because of the long stay of the hot water in it, the temperature around, and whatnot, the vessel remains in relative harmony with the water, because it's used to it. But if a anti-thetical, very cold gush water is rushed or surged immediately into it, a massive struggle initiates and the vessel is susceptible to breaking. Such too, I believe, is the human body.