Given we're getting into that, I should share some of my additional findings before carrying on.
So, reading into some stuff, I found more information pertinent to the hierarchy of universes that Marvel seems to sporadically apply here and again. This will be yet another addendum on the matter (
Last addendum seen here). For reference, the following comes from the early 2000s run of X-Man.
Basically, in X-Man #68, we are introduced to the concept of the Spiral of Worlds. Long story short:
It's the multiverse. To get more specific: The story tells us that all parallel universes are arrayed in the shape of an ascending spiral, a double helix, where Earths become increasingly good and perfect as you climb up the ladder, and, likewise, increasingly shittier and more primitive as one climbs downwards.
The explanation for why universes arrange themselves in this specific shape is given in the scans: As Above, so Below. The Spiral is, in fact, a genetic code. It's the DNA of some unimaginable higher entity. Admittedly I at first figured this being would be the Multiversal Eternity, since recent comics often analogize individual universes as being like his "cells." But given how obscure of a character he was in that period of Marvel history, this explanation seemed overly anachronistic to me, so I decided to look further.
And it turns out my suspicions were correct. The same storyline also introduces us to an important location,
the Brilliant City; this is basically supposed to be the highest universe in all of the Spiral. It's the pinnacle of anything that humans understand as "reality," where the most perfect beings in all the Earths exist. Said beings, for the matter,
being powerful enough to destroy whole Earths on their lonesome.
However, it's eventually revealed that, though it's the pinnacle of the Spiral of Worlds, the Brilliant City isn't actually the highest universe.
There is a spectrum of Earths even further beyond it, which Nate Gray
was completely unaware of, despite the fact he previously had the entire Spiral shown to him. The entities inhabiting these Earths, as it turns out, are so great that the people of the Brilliant City are, to them, even less than the lowest being in all of the Spiral is to the people of the Brilliant City (So, as Low 1-As are to Tier 10s, they are to Low 1-As)
Given how these higher beings are drawn as having bodies containing stars, and their position relative to the Spiral, it would seem that the Spiral of Worlds itself is supposed to be the "genetic code" of one of them. So, this is another showcase on the full extent of the Marvel Multiverse being a regress of levels, each containing the other.
(By the way, this also means that feats/statements like "He destroyed the multiverse!" won't inherently be High 1-A without further context, since there's a whole
hierarchy of multiverses in Marvel, technically speaking. Such feats will only be High 1-A if it's clarified that they affect all of Eternity)