Sigma is an extremely weird verse that looks like regular outer space. The reason is because it’s Quarkic with the space that can be seen from Earth. The reason is unknown. This is even kind of hard to see with even the Yellowmarkers Telescope. It’s still possible though. You cant see EVERYTHING with it, unless you have some kinda bionic eye. It’s made of lots of huge stars and those are all of those white dots.
It wasn't originally contained by the Primordialverse because there was repulsive matter in the Sigma. The repulsive matter started coalescing in one spot, and that started messing with the dimensions of the Sigma. Later the repulsive matter became way too much, and it exploded, sending repulsive matter everywhere. The dimensions still weren't fixed, though.
One thing that is special about Sigma is that its dimensionality depends on which angle you view it from. That can be quite confusing. If you are viewing it from a certain angle, the dimensionality won't change for anyone else. The Sigma duplicates each time someone views it from an angle it has not been viewed from. Each of those duplicates is for 1 viewpoint of the Sigma. (I know that this is extremely confusing)