Eidolon

Eidolon manifests itself as a planet so that the realms can be together physically. Each realm is surrounded by what the ghouls call "The Empty/Nothing", an ocean of pure void that prevents ghouls from going to other realms physically. However, there is one being that can float amongst the void: Charon. Known by livings as the ferryman for the dead, he is a massive monolith of a creature who ensures that souls get to where they belong. He is the only one who can manifest in Eidolon's physical plane and boat ghouls to other realms without issue.