Imagine an ideal box, whose contents are perfectly isolated. Whatever is inside it, it has not, has had or will have any relations with the rest of the universe. We could say that its content does not exist in our universe. It can have any form elsewhere, because even though it does not have external relations, it can have internal ones: inside the box there could be a beetle, the void or another universe.
Does the mere hypothesis of the existence of something in the "box" put it in relation to our universe? Is complete isolation therefore impossible?
Note: of course the box is an impossible object, because any box should have relations with our universe. This is why I intend the "box" metaphorically, like an isolated pocket of existence.