The Gargantisphere is the universe of all Gargantis realms and the portals that connect them — the whole interconnected space the peer-to-peer network of nodes renders and maintains.
It is analogous to the World Wide Web: just as the Web is the universe of hyperlinked pages, the Gargantisphere is the universe of portal-linked realms. A visitor can travel seamlessly between realms — potentially with different physics, avatars, and authoring — exploring and discovering as they go, without ever contacting a central server.
No node owns the Gargantisphere; it is the emergent whole of every realm being published, replicated, and explored across the network.