Universe Cluster

Universe clusters are, as the name suggests, clusters of Universes. A Universe cluster is a group of Universes (2 or more) that are all bound and dependant together on a common property. As in, if this specific property were to change in one Universe, it would also change for all other Universes within the cluster.

This is a very vague and imprecise definition that is adjusted for the english language, as creating a strict definition that applies across the entire Omniverse in scenarios one can't even imagine is simply impossible.

How Universes cluster
Clusters of Universes come in any formation one can and can't think of, so the ones discussed below will be of those that are most common in our general vicinity.

Terminal Spheres
A Terminal Sphere is a non-existant sphere that acts as a boundary for Universes packed together through gravity. The Terminal Sphere is a byproduct of the laws of the Multiverse, and whilst gravity exists in many places beyond our Metaverse, the Terminal Sphere can only naturally form within our Metaverse.

Terminal Spheres located on the edge of our Metaverse don't even work properly, with their sizes peaking at below a singular Universe, thus making these types of clusters impossible.

Rings
In a large group of Multiverses located in a neighboring Metaverse, gravitational forces created by the result of an average between two or more Universes is attractive, whilst that of one Universe is repulsive. This means that there are tons of extremely weak gravitational attractors located in random pseudo-random places, but it is also possible for a bunch of Universes to line up correctly, and perpetually spin in a ring formation.

The specific arrangement required for such a structure is very, very rare, but with the amount of chaotic movements caused by the Universes due to borderline upredictable movements of gravitational wells, as well as the sheer number of Universes and the length of time these phenomena have occured for, every Multiverse in this large group contains at least three.

This structure is very stable, as any disturbance will simply make the orbits more elliptic, and the gravitational forces will eventually smooth them out back into a circle.

Narzinil System
A Narzinil System, named after the Multiverse that contained the first observed one, is a system of Universes each orbiting the same point located in a void. This point is akin to a black hole, having escape velocity greater than light in vacuum, but it is completely independent of mass, charge or spin. It is merely a point in space. These points in space are called fixed black holes, and they occur only in closely scattered Multiverses in two nearby Metaverses.

Universes orbit these fixed black holes in the same fashion as stars would in a the very center of a galaxy. However, the gravity of these fixed black holes is unlike gravity, in which it extends out forever, slowly thinning out, but instead becomes an imaginary value that does not affect the Universes and is equivalent to 0.

A long distance away, this function describing the attraction becomes real again for a very short period of time, going then on to become imaginary for any distance. It is thus theoretically possible for a Universe to orbit at this distance, but the eccentricity would have to be too close to 0 for anything realistically achieveable.

Repulsive Universes
On rare occassions when gravity is both repulsive and attractive at different distances from an object, it is possible for a collection of Universes to carefuly cluster. In a long and thin stretch of Multiverses in a distant realm of our Metaverse this scenario plays out neatly, as Universes keep a distance from each other whilst attracting one another at once.

These clusters are fragile, but they are stretchy, in a way. Easily disturbed, but the Universes tend to come back even after travelling long distances away.

Effects on the Universes
It goes without saying that, at least in the examples listed above, clustering Universes puts them at a much increased risk of hitting another Universe. In a Terminal Sphere scenario, multiple Universes have to collide in a short amount of time and avoid destruction whilst at it, which ends 80% of potential Terminal Sphere clusters prematurely.

Getting past the difficult beginnings of a cluster, the structures remain very steady and the chances of any large scale damage resulting from collisions, although the chances may look unfavorable due to the chaotic nature of some of the clusters, are very low to none. In the case of the repulsive Universes, being located behind a layer of Universes the chances are literally none, as Universes within that region are not capable of naturally achieving velocities capable of breaking through the repulsive gravitational force near the Universe, and even if one did, the Universe mentioned above is still protected and affected indirectly.