The first empty plane of the underworld. It is a plain grassy area with the exception of a basement entrance door that appears seemingly at random.
In Petscop 4, Paul finds what he believes to be a camera pointing at a floating disc in the distance. He comes to the conclusion that the disc is where the windmill should be.
When Paul visits the disc in his shadow monster state in Petscop 9, he finds the windmill has returned.
Theories
If the Gift Plane really is a representation of Heaven, then the Newmaker Plane is Purgatory. Both Purgatory and the Newmaker Plane are mostly empty spaces.
The Newmaker Plane appears in one of the secret loading screen images.[1]