I guess that Supernatural is kind of a meaningless term anyways. If it isn't artificial and it isn't natural doesn't that mean it's non-existent? If there is a God, I think that it is a sentience that has existed since the... well I don't think you can say that the universe ever really began but that is kind of a complicated philosophical point... but since the beginning of the universe. I am not sure if God would be of the universe or being part of the universe itself. I think that he\she\it set the universe into motion. God would be an expression of as the Zoroastrians say, "the creative principle", while "the devil" is the "destructive principle". As spirits go and such (which I do believe in for reasons I'm not going to go into) they might be a form of electromagnetic life - which IS theoretically possible. If I am wrong about all this, and yet there still is a God, the I would guess he is some kind of Boltzman Brain.
Also... It is perfectly logical to say you don't believe in something. It is a whole other matter entirely to deny it's existence outright. That is what bothers me. There are many Atheists that take this and make it into a declaration. A declaration of faith?
Oh also... If they told me that the IPU was those things... the trilogy of utterly meaningless terns. Then I would think that they were becoming a bit obsessed and had begun to ascribe superlative terms to it. I would think that they should calm down and try and be a little more level headed. I would also explain that those terms made no sense and hopefully help the person better define the thing they were trying to describe. If they said it's really powerful and knows everything blah blah blah, then I would be very skeptical and believe they were just passing on exaggerations. Another thing I would take note of is if anyone else claimed knowledge of the IPU and try and figure out where the idea came from. If only one person has ever known anything about it then I would say "I doesn't exist" even though it isn't logical, but nothing in life is absolute is it?