Sigma
Sigma, to put it bluntly, is a mess. A complete, utter mess, but one that proves to be interesting enough to keep around.
At the top of the trainwreck that is Sigma, like all metaverses, there is the Ultima, who refers to theirself as the AM. It's unknown what this acronym truly means, and everyone just sorta makes up their own name for the AM, but the most common name given to the AM is the All Mother. The AM is what Ultima refer to as an empath, which means that they have far more concern with the well-being of the occupants of their metaverse, rather than the standard of objective observation and non-interference that Ultima are expected to hold. More than that, they pick and choose their favorite occupants as well, which is what is often referred to as 'a recipe for total disaster'.
A layer down, yet the main reason for Sigma’s messiness, is the utter catastrophe regarding her Nexus and Anti-Nexus. Originally, there was harmony between the Nexus and the Anti-Nexus. However, the demigod of the Anti-Nexus, who is often referred to as Cain, decided that being forced to live in the Anti-Nexus was a raw deal, and found a way to break out. This caused conflict between them and the demigod of the Nexus, and a fight occurred between the two. This ended with Cain's victory over the other, where Cain consumed the other, and they escaped the Anti-Nexus to reside in the Quarter.
This led to an imbalance between the Nexus and the Anti-Nexus, which caused Cloud metaenergy to begin leaking into the Quarter. As a result, the Quarter is chaotic and unstable, and has been for eons. This could have been fixed early on by the AM, who would merely have to wipe the metaverse and start over, but they held a fondness for their 'problem child' Cain that stopped them from doing so.
For trillions of years, everything continued along. While the effects of Cloud energy leaking into the Fourth changed and shaped the development of the universes, it all managed to not fall apart and blow up spectacularly in the AM’s face, which could be construed as a success. Much as it should be, the different universes were more or less ignorant to the metaverse at large (with one main exception). That was enough to keep the AM satisfied.
Then the Great Unification happened. The Great Unification occurrence requires context, but, for now, it was effectively the result of one very disgruntled person figuring out how to utilize Cloud energy. In a great display of power, this person decided to pare down the amount of universes within the Quarter, from roughly an infinite amount to ten. Additionally, she revealed the existence of the megaverse to everyone within these ten, and linked the universes together through zones that allowed for free teleportation between them.
Thus began what can be considered the current state of Sigma. Ten universes, some similar to one another, and others that are insanely different, linked together, with people who communicate and work together as best as they can. For better, or for worse.
Sigma’s different universes are designated through labels corresponding with the Greek alphabet. The ten are named thus:
Alpha
Beta
Gamma
Epsilon
Zeta
Lambda
Nu
Rho
Psi
Omega
