I'm writing about demons who live in an alternate world that exists below our own. They rarely venture into the human world because it forces them into a solid body, which they find painful and unnatural.
I have two possibilities in mind for their natural state. The first is that they exist as formless shapes made of what they call "essence" and move around by floating, almost like ghosts. They don't really have a physical form in this scenario, and their pain stems from the fact they are not naturally solid beings.
The second is that they are shpaeshifters who constantly change form, and in this case, their dislike of bodies comes from their inability to change while in the human world. Staying in one shape for too long even in their own world can become uncomfortable, and it's very painful in the human world.
Which concept is easier to understand?