[**Spoilers for Final Crisis (2008-2009), Superman Reborn (2017), BATMAN R.I.P. (2009), Ivar, Timewalker (2015-2016), Crisis On Infinite Earths (1985-1986).]
I am not a scientist, and I did not major or minor in science when I attended college. However, I can say that I am good at puzzles, and what is a theory, but part of an unsolved puzzle? In this case we might look at the term “multiverse” and then consider how multiple companies/franchises have used the concept. If we then take a “real world” perspective and think about each iteration (DC, Marvel, Valiant, etc.) as being true, then we are left with a quandary: If all are true, and yet all are separate, how can something like Valiant’s The Null or DC’s The Anti-Monitor destroy or conquer the entire multiverse? (Ivar, Time Walker and Crisis On Infinite Earths).
One of three answers may have occurred to you in the space between the last sentence and this one. The most likely answer is that they are from works of fiction, and therefore subject to creative and corporate limits. The second possible answer is they exist in different two-dimensional multiverses with representations at each company or franchise. Answer three is simply that the multiverse is infinite. All three are to one extent or another probably correct from a scientific and layman’s point of view. However, I think one could go further and say they are all parts of the same answer.
If the multiverse is infinite than it could exist and defy dimensions and personal perspective. Case in point, the character Mr. Mxyzptlk as a fifth dimensional being shows in various parts of Superman Reborn that time and space are a matter of how one views things. Heck, Grant Morrison suggested in Batman R.I.P. that the fifth dimension is just imagination. Though neither example is provable (at the moment) via scientific method, it does seem to have a bit of credence found in the “real world” scientific theory of Biocentrism.
For those who don’t want to click on the link I provided, Biocentrism suggests that literally everything is a matter of personal perspective. Yes, there is more to that theory, but that is the main element that you readers need to take away. The reason for this is that by using personal perspective, we can see that the companies are only providing sections of the complete multiverse. Yet, what does this mean for the characters found in these sections? I theorize that no matter what form of media they exist in, they are as limited as we are to their respective sections of the multiverse. Thus characters like the Anti-Monitor and The Null are unable to destroy things in other sections.
However, where does imagination come back into the picture, and how does our reality play into things? I posit that our section of the multiverse is able to interact with these other ones due to our imaginations. For example, when we reboot, remake, recast, or relaunch something we are able to see different universes in sections. Thus alternate timelines are just alternate universes, and each universe is as separate as each section of the whole multiverse. Therefore Grant Morrison may be somewhat right in suggesting that the multiverse is a living thing. In other words, whatever the multiverse actually is it wants to live and is nearly impossible to fully grasp.
In conclusion, destroyers like The Null or conquerers like DC’s Darkseid are like geckos trying to eat a universe (Final Crisis). They just can’t succeed.