You said the universe is part of the Dream. What, then, lies outside of the Dream? Is that emptiness? 

To speak of “outside of the Dream” is simply a metaphor for “awakening” to the Dream as being unreal (even while one is yet within the Dream).

Obviously, there can be no “outside” to something which itself is not real, and therefore does not truly exist. Even though we speak of being “within” the Dream, because it is unreal, there is no actuality that is “inside”, either.

Emptiness cannot lie outside of, or apart from the Dream. Emptiness is form. When form appears, it is empty of reality, or existence. Form is emptiness. When a form ceases to appear, emptiness is no longer there either.

So it is not that the Dream is occurring inside a static condition called emptiness: emptiness itself is what form is (such as, the universe) during its duration. It is “why” phenomenon are without true reality.

Emptiness is not, therefore, a standing condition. It does not exist as “another” or alternative reality. And what is 100% empty cannot contain anything “within” it, or “outside” of it.