Long ago there existed many worlds in multiple realities, they one day started converging and eventually merged together into the Spiral. There in the center lies the center world, our world, which is the main hub for all worlds existing within the Spiral itself.
In the Spiral exists an infinite number of worlds within which lie different realities, every eventuality and concept imaginable exists as a world. Reality changes inside a world to fit whatever rules are present, anything is possible within the infinite spiral.
Rifts often form on the worlds both natural and otherwise, the cause for these are currently unknown but what can be inferred is the conversion has formed a weakness. natural rifts are rarely a whole shape and tend to be cracks in time and space which catapult the nearest thing into a different world. Artificial rifts are often spherical in shape and act more like portals instead of miniature black holes.
The central world was once Earth before it expanded in size and became the main hub for every world. Currently it exists as a place of dwelling for numerous visitors and other such things from other worlds. It is also the planet with the most rifts that form on it both natural and artificial. Numerous artificial rifts which are called portals have been created to visit and leave worlds at will.