Through the portals and gateways of the City wait an infinite number of alternate worlds to visit and explore. The entire Multiverse is just a step away for those brave enough to dare the unknown.
Whether you call them worlds, planes, universes, dimensions, or timelines, the Multiverse runs the full gamut of imagination. Prehistoric dinosaur worlds, starship galaxies, sword and sorcery kingdoms, cyberpunk cityscapes, furry cowboy ranches, steampunk Aztecs and robot Victorians... Anything you can imagine is possible, and can be found somewhere out there. The City has portals to a million different worlds and there are many more yet to discover.
Players are encouraged to create their own worlds, as many as they wish, to explore and adventure in. There is no official list of known worlds, and no approval process. Any you create in play are considered valid.
Worlds that are listed as "Available for Public Use" should be considered open settings, much like the City itself. Players may use the world however they want, but please be respectful to other player's and the world's creator when considering any massive changes to the nature of the world in question, as other people have a right to use it as well.
Worlds listed as "Available for Use with Permission" are considered semi-GM'd, and you should look for details in the Lore page about what the creator of the world wants. Typically this means the world can be visited freely with the creator's permission, but the creator wishes to keep tighter control over what happens in the world than in a Public Use world. This often includes "origin" worlds that are part of a character's backstory.
Worlds listed as "Not Available for General Use" are usually tied to a specific campaign or character. Typically such a world can only be visited by participants in related campaigns.