Originally written up as a comment on another post (here ), decided to post it as a separate post to get feedback.

What happens during sleep?
What is sleep paralysis?

At this time we only really have theories on what sleep and sleep paralysis may be, but there is a lot of different theories and this is one of mine.

I am of the camp that when we dream, we are seeing into another realm of consciousness where reality is a bit more "fluid" (so does not always make sense to our minds of this reality) but for the most part we are just passive viewers of the alternative reality. We have a "persona" that exists in that reality but we have no real control of that persona, it is like our personas are on "auto-pilot".

When you become capable of "lucid dreaming", it is you taking control of your "alternative reality persona" and you can begin to affect what occurs in that alternative reality.

Sleep paralysis is like an bad connection on a phone line. Your "minds eye" is seeing the alternative reality, but because the connection is bad it is resulting in a "bleeding effect" that is overlaying that reality on this one.

The "monsters" that we see may not actually be monsters, but may be due to the bad connection distorting the images. If the connection was good, then the "monster" could actually be perceived as something else. For example during one sleep paralysis episode, I watched various animals with full detail, running around my bedroom.

Then we have what we call "Out of body experiences" (OBEs). Most often this is not associated with monsters or anything bad, but we basically see ourselves outside of our own bodies. Many people see OBEs as a manifestation of our internal spirits, but I have the theory that what we are actually doing is a reversal of the connection to the other reality. Rather then us taking control of the "alternative reality persona" in the alternative reality, we are actually pulling that persona into our reality and have control over it.

In some cases, we may not have complete control over the alternative persona in our reality, but we can make unconscious "commands" to it.

TL:DR - It is all in how we perceive things.

EDIT:

If we bring in the multiverse theory, dreaming could be our method of traveling between these different realities/universes. The further we get from "norm" (this reality) the more "confusing" we see things in other realities/universes.