I’m writing this really early in the morning so I hope this makes sense…
What if the Domain is connected to lifeforms in the galaxy? It’s said that the Precursors believed that the Mantle extended to the entire universe which included energy, matter and living creatures. Life-patterns and living wisdom collected by the Precursors over a hundred billion years was stored in the Milky Way galaxy as a reserve. According to the Gravemind, the Domain is an immense field which is projected by the reserve itself. Most would think that it’s projected by the Precursor structures themselves, but it’s said that the Precursor structures were added to this reserve to protect it.
Halo: Silentium
String 37, Page 322
“This reserve was wrapped in Precursor architecture, protected for many billions of years.”
So this doesn’t mean that the structures themselves were solely responsible for projecting the Domain. Think about it. Precursor structures weren’t the only thing destroyed by the Halo Array. The galaxy was completely cleansed of life. This could actually explain why the Domain has appeared to suddenly return. After the Array was fired, the galaxy was reseeded and life began to grow once more. Over the course of 100,000 years, the galaxy may have reached a population level capable of sustaining the Domain once more.
There is also this interesting bit of information that Catalog learned from the Gravemind in Silentium.
Halo: Silentium
String 24, Page 208 - 209
“During our debate, the Gravemind hinted at a vast reserve of rules accumulated more than half a billion years ago, a huge library of experiences and disputes codified into the total wisdom of the Precursors.
I am there. I can see it, judge it! It floods me with case history.
The High Juridical was correct! Those who created us, who formulated the very concept of the Mantle, were themselves rich with distilled precedent. I can see their rules written in our genetic codes! We are creatures of Precursor law down to the very chains of molecules within us.”
This reserve of rules accumulated by the Precursors was collected and written in out genetic codes. Life is what projects the Domain and that’s why it’s back. Of course now you have to wonder how Cortana was able to access it by falling into slipspace. Consider this: It’s believed that the Domain served as a type of afterlife by the Forerunner when a person’s essence would pass into it upon death. In Silentium the IsoDidact would wonder if there was any distinction between machine and living beings.
What if the Domain doesn’t actually see a distinction between the two and that’s how Cortana survived despite death? When she died she may have passed into the Domain and made contact with it as any organic supposedly should. She says she made contact with it after being pulled into slipspace, but remember Doctor Halsey’s experiment where she believed she could create an abstract fractal structure within slipspace which would allow an AI to be stored inside. We don’t know the details of this experiment but it would seem that Halsey thought of a way to access the Domain without even knowing what the Domain was at the time.
In Silentium we learn that the Domain is apparently alive. It opens itself and testifies to the Senior Juridical. That intelligence appears to be missing for some reason in Halo 5 but there could possibly be an explanation for that. The Flood is controlled by a central intelligence we call a Gravemind, but it can’t form a Gravemind until it has collected enough intelligence and biomass to grow. What if the Domain works the same way? Intelligent lifeforms will cross over into the Domain and when it has collected enough, it forms a compound mind. This is why it was intelligent in the past and may have been the one who reached out to Bornstellar when he first made contact with the Domain. It’s open now but it might not have enough minds to form a central intelligence, which is why Cortana appears to be in control of it. This could change if it collects enough AI.
I almost wonder if the Flood is actually like an Anti-Domain which exists in our physical world, as opposed to the Domain which exists in the digital world. It was hoped that the Composers would bridge the gap between these two worlds. However, do you remember when the Librarian said that life forms who were digitized couldn’t be returned to organic form because it only created abominations? What if that’s what the Flood turned out to be? The Primordial could have been an example of a digitized essence, or essences, that attempted to return to organic form. Instead they only created an abomination and that creature would become the first Gravemind.
I consider the Flood to be a sort of “Anti-Domain” because they’re similar, but the Flood is apparently capable of corrupting the Domain. When the Flood collected enough biomass to form Key Minds, they were able to reach out and seize control of the old Precursor Star Roads. They would them manipulate slispace, which the Domain resides in, and form it to their own needs. This would make Forerunner drives completely useless.
Halo Silentium
String 27, Page 236
“Space-time in this region is mutating to suit Precursor transits - the Flood is headed for the Ark. Slipspace here will soon become incompatible with out drives.’
‘The scale!’ she exclaims. 'Even slipspace is corrupted. Is there not a pure thing left in the galaxy”
It’s getting late, so I’ll try to summarize this. The Flood and the Domain are extremely similar to each other. One is organic and the other is digital, but both collect the intelligence of living and artificial minds to form a central intelligence. Both the Flood and the Domain were damaged when the Halo Array cleansed the galaxy of life, but now that life has returned and they are both able to regrow. The Flood created a Gravemind once already but now it’s time for the Domain to open and grow. Cortana however has taken control of this adolescent Domain and used it to bring digital only minds to her.
Cortana may very well serve as the basis for the compound mind that’s supposed to form. I’d like to think that this happened to the Flood as well and that Graveminds are actually the minds of the Precursors who turned themselves into powder. When they gain enough biomass and collective knowledge, their minds form and take control. Cortana could be doing something similar and she will assimilate the AI who give themselves to her and form the Domain’s equivalent of a Gravemind. Wouldn’t that be crazy.