Despite Revelations giving what most fans considered a "lackluster" and "terrible" ending to the Zombies saga we've come to love, lots of light was shed on many open questions that we originally could not answer prior to Gorod Krovi. And this doesn't reach just into Black Ops 3, but BO AND BOII as well. Let's take a look at what we can tie up right now:
Universe vs. Multiverse
In the beginning, we almost certainly believed the entire Zombies story to take place in one, single universe. There were hints via Kino der Toten that an alternate universe was possible, but many refused to accept it without more evidence. Once Origins and Mob of the Dead came along, that hard-headed thinking changed drastically.
Monty himself claims that we live in a multiverse, yet inhabit one single universe. There have always been multiple universes - but we just never had a problem with it until now.
We understand that the universe was fractured; however, not in the way we thought it was. According to Monty, everything changed when Group 935 started experimenting with teleportation. The very fabric of time and space itself began to tear, as per the only thread that held it: Element 115.
Y'see, Element 115 is not meant to have existed within the physical dimension. It's more of an ethereal, non-physical blanket that encompasses the multiverse to keep everything linear and connected, but not open. When our universe got their hands on the element (somehow), we kept creating tears in time/space itself, allowing other universes to bleed through.
This is how the Apothicons devour universes: sending Element 115 into universes where it doesn't belong, forcing a tear to open up as a gateway. Once the tear is large enough, they can enter the universes and begin consumption. This leads into another interesting concept.
Aether & Agartha
Leading up to Black Ops 3, we had strong in-game (and theorized) evidence that Agartha was a mythical place within the middle of the Earth, and the Aether was a metaphysical dimension that held passage through time and space itself, allowing one who inhabited its domain ultimate power.
Unfortuantely, Monty also mentions that they are both the same. This isn't just true for one universe, though - this is for the entire multiverse. No mortal should be able to access it, let alone a metaphysical one. What does that mean exactly?
Despite being almost all-powerful and practically god-like beings, both Monty and the Shadow Man can't hold their presence within the Aether. How could that be? It's hard to tell...but it seems that they do not belong in that dimension due to the erratic stability of the realm.
We aren't in Monty's perfect world, or even a distorted version of it: we are actually within the Aether itself. Bits and pieces from other maps are sucked into this as a result of the Shadow Man opening a portal inside the Aether, causing instability and further fracturing. This is not a natural phenomenon, hence the severity of it all.
The Children and The Souls
All of Black Ops 3 revolved around collecting the souls of each 1.0 character...or was it? We understand that our original characters were most likely dead or simple MIA after the Moon events. Looking at the different BO3 maps, we see that these 1.0s are NOT the same original characters we grew up with. But why would they be important?
Back in Shadows of Evil, Richtofen wrote on the torn scraps that he was chasing the wrong leads, instead finding coordinates to each future map location exactly where our targets were located at. It should also be mentioned that not all of these intended targets resided within the same universe (for obvious reasons).
While a long shot, the main goal of collecting the souls was NOT the insurance policy. We know that the blood vials are just that; the souls, on the other hand, are actually descendants straight from the Primis crew themselves. Hence, why their souls are chosen to be within the bodies of the children in the House. This perfect world, as created by Monty, would compose of himself, four children with the souls of ancient warriors who vanquished the greatest evil in the known multiverse, and somehow Maxis/SOPHIA.
The only contradiction we face is Richtofen 2.0, who Monty claims doesn't have his soul. Hell, he isn't even sure why he doesn't - all he knows is that his 1.0 soul was filled with evil. Could this mean that no matter what universe they were to observe and soul to collect, Richtofen was destined to be evil at the end of it all.
Now, a glaring problem: Eddie resides in the house. Well, at least what we believe to be Eddie. In the one of the past map radios, we hear Maxis talking about how Monty brought back Samantha and Eddie. But something was wrong...Samantha was no longer the same as she originally was. Perhaps when those children died, their souls also departed and thus, Monty could only create shells for them until everything was restored?
Now why would Primis' souls be scattered? The same reason why the Keepers were also scattered as well, as mentioned in the earlier Monty quote of this thread. Element 115 experimentation and teleportation simply fucked everything up, as blunt as I can put it. This is why our 2.0 crew has to hop through time, originally believe they could just stop every Ricthofen they came across with minimal aid from Maxis. At least, until Richtofen came along and led them to the true mission.
Would love to hear any other loose ends/comments! There are many still that are waiting to be explored!