A hubworld is a type of universe that is particularly well-connected to the other universes within its multiverse. Portals and space bridges between different universes and the hubworld often form, letting objects or even sentient beings pass through.

Since it is possible that highly-advanced civilizations will eventually discover hubworlds and realize what they do, it stands to reason that they will go about making their local hubworlds habitable for all forms of life across the multiverse. Perhaps gigantic megastructures like Dyson Spheres or Alderson Disks would get constructed to provide habitation, or a web of physics-defying towers and pathways, kiloparsecs tall and wide, might be built that span entire superclusters. Of course, any reasonable civilization will also construct defense mechanisms, including hiding the hubworld away so that the "primitives" inside cannot be detected or harmed.