Ok so I finally finished Tenebra.
e: Ok, so an initial thought that I don't think anyone here has produced so far IIRC. The Vishnans talk about an apocalypse and how the Protocol was forged then, and then mention the "Summed Psyche". There is random mentioning of the noosphere and so on (when the Shivan node first mentioned how the noosphere was being subverted, I thought it was talking about how the Vishnans were subverting humanity).
Now, I had misread the term "Apocalypse" as if a great galactic war had surged eons ago and to prevent it a new "Protocol" was created. I was obviously confusing two very different events (the "Dawn War" and the "Apocalypse"). Apocalypse is not, in its original greek, a "disastrous destructive event" per se. It actually translates to a "disclosure of knowledge", or in more biblical terms, Revelation of the Ultimate Truth (and thus the end of the world and so on). Right afterwards the Shivan refer to the death of Brahmans and the "making" of the Vishnans.
So here's my initial interpretation: After this (still to understand) first "Dawn War", the Brahmans reached enlightenment. With it, they created the first noosphere, and this event is referenced as "the apocalypse". We can think of it as a special case of Singularity, which involves the control over Subspace (and therefore time and therefore travel between universes and other crazy abilities we already know of) by a gestalt composed of the entirety of the Brahman species' consciousness. That thing is now called "Vishnans". The Vishnans were "made" in that event and thus the "Brahmans" disappeared. The Vishnans are the transcended Brahmans.
The Shivans have a similar "anima". We could speculate (or not) if this anima was born out as an autonomic response to the sudden appearance of the Vishnans (as a kind of a super strategy against "godlike" creatures like the Vishnans), but then we also know that the Vishnans seem to try to convince the Shivans they speak for the Terminal Protocol, which is something that apparently the Shivans think is very important. However, they also reach the conclusion that the Protocol has failed. Failed to do what? The Brahmans' bidding. So the Shivans are both serving the Brahmans' wishes (which would indicate they are a creation of them) and are also eternal ("calculated", "eternal").
There's an apparent contradiction in here. It may be solved in two ways. The first involves a bit of convoluted writing. Here it goes. The definition of the Vishnans is one that allows them to observe the "past, present and future" all alike. Thus, even if they "came about" when Brahmans transcended, they can "see" and "influence" at every single time in the universe as they please. And they can calculate a new "species" that lives "forever" in this spacetime like a supercharged Von Neumman like species with "immune system" characteristics as MP outlined a few days back. In this fashion the Shivans could have been both eternal and a creation of the Brahmans. This is, however, inconsistent with the fatalistic observation by the Shivans (they watched Brahmans come and go, they will have watched the Vishnans go away too).
The second way is to say that the Shivans are indeed independent from the Brahmans, but their objectives aligned against a common threat. The threat of the Cognocide.
So, finally, we get to my wild speculation. The First Apocalypse was the Singularity of the Brahmans. It was a marvelous creation, that of the Vishnans. The Vishnans now exist in a transcendental state, in subspace no less, within an enlightened "noosphere" called "Summed Psyche". The unexpected side effect was that this event "ended the world" for the conscient beings all over the galaxy/universe. It was a "cognicaust". And so the Brahmans died. And for whatever reason, the Shivans didn't like this event at all. And so a Protocol was formed between the Vishnans and the Shivans, a kind of a deal that allowed the Vishnans to capture whatever kind souls would reach enlightenment to its Summed Psyche before they triggered a "second apocalypse", and allowed the Shivans to destroy whatever infecting "Hegemon" the Vishnans would deem "unworthy" before those triggered their own apocalypse.
Since the war started in Sol, the Vishnans finally gave up completely and ordered the cull. However, the Shivans are not playing their part due to an external heuristic. Some guessed this "external heuristic" was Bosch. I haven't decided yet. What is striking is that the Federation's "ultimate" weapon is nicknamed "Shambhala" whose wikipedia page is phenomenal. I could go out on a limb and say that it would be so ****ing cool that Shambhala was a Singularityzation machine, thus provoking the second incursion of the Apocalypse. However, this would be an affront to both Shivan and Vishnans, so it's somewhat inconsistent with the Vishnans refusal to mess up with the Elders to stop it from happening or the Shivans apparently being all-okay with it.
Still, I think the morality play here will be about humanity's redemption, about the ideas of the singularity, the danger of complete Cognicide (local or universal), the questionable morality and rationality of the Vishnan gatekeepers and the utter amorality and unconsciousness of the Shivans.
