Well anon, I’ve heard this before, and I know people have been polite when they decline. I’m going to explain why this cannot, or more, will not happen.
One, we know nothing about this person and will not harm anyone who does not deserve it.
Two, even for a demon there are consequences to our actions and there is simply no way in hell (pun completely intended) you could make it worth our while.
Three, do you know how complex and intricate normal incarnation is let alone switching into a currently inhabited body, and an unwilling one at that.
Four, that would take enough power to kill a human being, it just wouldn’t work, you’d burst into flames before you even got halfway there.
Five, an incarnated demon does not have access to even a fraction of their power and so would not be able to accomplish this.
Six, a none incarnated demon would either say no or screw you over so hard your head would spin.For these reasons and many more I suggest you end your quest and maybe think of another, more sensible, way of getting what you want.
I’ve seen a few people get this ask recently. I don’t know if its a troll or not