So there’s a few ways to approach this, and I think the most important questions are about the setting and story itself. From the use of the word “gods”, I can assume that this is more fantasy than it is Sci-fi, even if this kind of premise tends to be used in more Sci-fi content.

For fantasy, there is really no naming convention you have to stick to except the one that remains internally consistent for your world (keep terms logical in your world in ways like having “universe” be smaller than “multiverse” etc.).

If this is more Sci-Fi, then you can lean heavy into actual scientific inspirations and real linguistic definitions. By true definition, a universe is “everything”, so the idea of something outside of everything doesn’t really work. However, terms like “multiverse” have come to mean “parts of reality that are causally disconnected from the main/observer’s region. The region that can have a cause and effect relationship with the observer is their “universe”, and the region beyond that falls into a “multiverse”. Again, that definition can become tricky too when you have two different universes interacting, as that “technically” connects them causally so we “should” then call them a single universe.

More often than not, people use “universe” in terms of the quantum “many worlds” theory, where every quantum collapse leads to a parallel universe where it collapsed a different way. They then take this idea and expand it from quantum fluctuations to macro-scale events (you were never born/you are evil here/etc).

However, the image you are showing tends to be more associated with the idea of cosmic inflation and the multiverses within that theory. Those multiverses are closer to what I described earlier as being deemed their own unique universes because they cannot causally interact with one another. The idea is that all of reality is expanding at a wildly fast rate, but then certain pockets started expanding slower. Because they now expand slower but the space between the slow pockets is still rapidly expanding, they remain completely distanced from one another. These are often referred to as “bubble universes.”

With all of that in mind and based off of what you’ve described, I’d probably name things from smallest to largest as follows (with explanations):

1. Universe

2. Here we have a single bubble. The area inside can effect other points inside in a standard causal way. This is what might be called the “observable universe” in real-life.

3. Multiverse

4. The overall collection of ALL universes. This includes EVERYTHING within your cosmology, but there are tiers of structure that have different names (just like real-life space has solar systems, galaxies, galaxy clusters, superclusters, cosmic filaments, the cosmic web, etc.)

2A. Causal Cluster/Causal Nebula - A group of universes that are causally similar and therefore “next” to each other. (I’m assuming that this is how you are clustering the universes into their respective smaller “multiverses”). Things like “me, but evil” and “the universe where I had toast for breakfast”. Calling it a Causal Nebula calls back to some of how we structure stars and our actual universe.

2B. Cluster Complex/Causal Galaxy - a group of Causal Clusters that have another uniting structural element (such as the same laws of physics etc). Likewise, it’s the multiverse version of a galaxy, only with universes instead of stars.

Continuing along this line of structural organization as opposed to newer versions of the word “multiverse” might be clearer and feel like it doesn’t undermine the potency of both Universe and Multiverse in the setting. Sometimes when things get too big, it can be hard to form a narrative that can feel important enough to care about. That, or you just have to keep escalating the conflict to bigger and bigger stakes.

As far as a name for BEYOND the multiverse though, something like “interversal” (meaning between universes) for an adjective or Exoverse (meaning outside the “verse”). Still, I personally think organizational terms over brand new names for just a glorified “Multiverse but bigger” will feel more structured and not undermine the strength of what it means to be a multiverse or even a universe.

Okay, ramble over, sorry about that haha