The Multiverse is a term to describe all of existence accessible to non Transcendentals.
StructureThe Multiverse consists of eleven dimensions. The Structure of mathematics orders all of these dimensions. Every universe within these eleven dimensions is 6 dimensional, which means there are just alternate timelines, not different start conditions for every timeline in a single universe.
There is a smaller universe for each dimension. For example: the three dimensional multiverse, where our's exists in. All of these separate, (if you exclude alternate timelines) smaller multiverses are seven dimensional, which means that it is a plane of all possible worlds with different start conditions. With alternate timelines included it is 8D, which in turn means that these universes have nigh infinite amount of alternate timelines, which varies the possibilities in each of these universes. The afteruniverses and higher dimensional multiverses are nine dimensional. Their history is different from our multiverse (except the "Core Events") and they have different laws of physics. The Tenth dimension is the plane of infinity, and the eleventh and last dimension is the place from where you can observe everything. It is also the plane where you can contact with the Transcendentals.
At the beginning the multiverse was created through the collapsing of a multiverse before ours. Shortly after it's birth it was chaotic. There were just a few species that were able to evolve at that time.
The greatest and most influential of them is a race known as the Grofix. They banned most of the Chaos of that time. Set up the laws of the new multiverse and engineered one of its most fundamental parts:the Space-Time Continuum.
The surviving Chaos beings were angry about these changes. They fought with the Grofix for billions of years for the domination of the multiverse.