The Cluster is a huge complex with many Collections at its center.
Structure and Layers
All of 500 million Collections that The Cluster contains are at its center. That creates an extremely dense center of gravity, and The Cluster is constantly pulling things into the center. This layer also appears extremely white, and it gives off huge amounts of radiation. Still, the creatures inside The Collections aren't affected by the radiation at all.
The Gas Layer
After the center is a thin layer of gaseous Toxicium. That also makes The Cluster appear quite blue. Even though this layer is not very dense, it still poses a safety hazard for creatures attempting to travel outside of The Cluster.
The Space Rock Layer
After the gas layer, there is a layer of space rocks, dwarf stars, small verses, and small planets. It is unknown why this layer exists; one theory is that The Cluster used to be encased in a solid shell of sorts, and then The Collections at the center of The Cluster broke it with their immense gravity. However, that theory doesn't explain everything. There have been mining operations set up by unknown creatures in the outer regions of The Cluster though. Many planets, stars, and even verses have been mined completely. This layer is just a brown/black color.
The Final Layer
The final layer of The Cluster is a thin but extremely tough layer of unknown material protecting The Cluster from outside threats. This layer seems to have a few dents, possibly from outside life trying to break in. Also, this layer appears to be a translucent color.
The Outer Layer(?)
The Outer Layer is a theoretical layer that might exist beyond The Final Layer. This layer is thought to be completely alien, with unknown laws, materials, and creatures.
There is life that live in The Space Rock Layer of The Cluster. This life is quite advanced, and has frequently mined the planets there for energy. This life is extremely resistant to cold temperatures, and has a tough exoskeleton. The life hasn't been contacted as of writing.