The only beings that can exist here are Boltzmann Brains, as they exist on the Multiversal Fabric. Most of these Brains are Free Minds, which are further divided into different types.
How the natives perceive the Between is unknown, since spatial entities would be unable to comprehend that information. However, Free Minds are more than willing to display what the Between looks like in ways spatial beings can understand. The resulting image is a pure black void.