What lies beyond the observable universe?
Nothing, as far as we know.
The observable universe extends 45 billion light years in all directions. However, that does not mean there is more of our universe to be found beyond that distance. As of now, it is about as far as we can "see." That may well be the boundary of our universe or it may extend for another 45 billion light years, we just do not know.
But if you are asking what lies beyond that boundary where ever it is? Nothing, as far as we know.