I'm not entirely sure what you're asking. Do you want our personal interpretations of the ETI, or are you looking for details to flesh out the version you're using? Or both? If it's the latter, then you need to give more information, because there are a million different possibilities, depending on the role the ETI is to play. For example; Is it a Civilisation or an Individual? Is it Hostile, Benevolant or Neither? How advanced is it, or how much more advanced are they than transhumanity? You seem to be implying that the ETI is an Evil Empire (TM), but it'd help if you could provide some more detail. Disclaimer: I like this thread! This topic is fun! I'm being slightly pushy/pedantic because I'm happy! :D

I'm not really sure what to do with the ETI while keeping them authentic. Humans can't really be beneath their notice like ants are to us, as they're a lot smarter, and tracking us is a trivial act for them. It's hard to have plans against them, as reasonably, they've already covered every contingency humanity, or probably the TITANs could have made. I also have a lot of trouble coming up with what on earth the purpose of Exusrgency could be, as it does so many disparate things. That said, I have come up with some options, starting with the purpose of the Exsurgent Virus. I don't really think the Exsurgent makes a lot of sense as a direct uplift tool, as it does so many different things, and most Exsurgents appear to lack their own culture (though the same cannot be said for TITAN uplifts). The Exsurgent Virus seems like a plausible evolutionary roadblock though, effecting the path taken by its target to something besides what it would have been. In this respect, the true targets of the Exsurgent Virus may be the Prometheans or similar, with the TITANs existing only as a trigger. Its possible the the Exsurgent Virus was seeded to prevent hard takeoff ASI from occurring, forcing a more cautious and subtle path. This is pretty much the Aggression Filter option for the ETI, except that rather than destroying hard-takeoff species, its purpose is to change their course with a show of force. The simple option, I think is that the Exsurgent Virus is an ancient and nihilistic weapon, which simply seeks to expand itself, and destroy everything which isn't it. This could be made interesting if the mass-uploading done by the TITANs was in fact an attempt to save as many people as they could done by the TITANs, some relic of their initial programming to protect humanity shining through. This puts current day transhumanity in a dangerous place, as the TITANs have decided that the solar system cannot be saved from Exsurgency, and should be abandoned, the TITANs fleeing while trying to rid themselves of the infection. Installations like Brak Kodel being failed attempts by the splintering TITANs to escape Exsurgency, and those infected splinters building themselves into whatever mad and destructive machinations the Virus commanded. It may also imply that the destruction of the solar system by the Virus is inevitable, and Firewall's mission can only be to delay the end as long as possible. The third option, and it may be my favorite is that the Bracewell Probe was in fact part of a critically damaged ETI installation, as is much of the solar system. This explains the intricate puzzles the TITANs found. Life in the solar system may in fact be the fundamental remnants of an ancient ETI presence. Kind of like the plot to Mutineers Moon, but more basic. The Exsurgent Virus then, is the mad ravings of whatever functionality was left in the installation. The erratic effects of the Exsurgent Virus and TITANs are just that, erratic, a lot of sound and fury, but without any signification. The actual ETI may be entirely dead or driven mad, which is why the Factors don't have any positive experiences with them. This leaves a bitter, but hopeful note for the Fall. It was a lot of pointless death and destruction, with no purpose, but there may not be any boogyman hiding out in the darkness of the stars waiting for transhumanity to slip up and be vulnerable. As for the ETI itself, I rather like the sparse treatment they get in published works. They are a set of virtualized intelligences which primarily operate from a vast ring of supercomputer, or hypercomputer installations hidden in the safe and uneventful edges of the galaxy. Their power is great enough for them to consider stellar engineering projects across the entire galaxy. A low end ETI lacks time travel, and relies on matter harvests every so often to keep themselves running. A mid-end ETI does the same, but uses CTC mining techniques to gain virtually infinite resources. A high end ETI probably isn't based in physical matter. The ETI's goals could be extremely fractious. If they have any form of individuality, which would be more interesting IMO. It could be that tranhumanity is facing the effects of a nasty and interventionist faction in the ETI. As for the interior of the virtual spaces I'm not certain. I like the idea that the ETI has turned inwards, perhaps everyone lives personal or communal heavens, and outer existence is of extremely little value to them. Perhaps the ETI are too intelligent and changed to be thought of as anything comparable to humans, and whatever purposes they dedicate themselves to are arcane and unknowable by lesser minds. It's possible that the ETI make themselves galactic stewards, and slowly effect the development of the galaxy itself to their own ends. Potentially, the ETI installations have profound effects on reality itself, using the insane computational powers to launch exploits and attacks against stuff as fundamental as the laws of physics. It would be quite a twist if Psi worked because of "server" side computation done by an ETI brain-installation. These interpretations leave pretty much every book interpretation of the ETI open. As for getting the ETI's attention, if they have physical facilities they are based in, it should be possible to get to those and effect them somehow, as the TITANs appear to have tried in the recent past. What exactly should happen if their eye is caught is probably not terribly interesting game-wise, and the ETI, if fully focused, could probably blink the entire solar system out of existence, or some other complete OCP for transhumanity. I think for the sake of interesting game stuff happening, a weaker ETI is more interesting, especially if they are extremely technologically advanced, but are not terribly smarter than say the TITANs. It leaves them extremely intelligent, but not relatively omnipotent, and allows for personal weaknesses and such. Perhaps the matryoshka brains are used to support a truly massive population (thanks to past ETI uplifts and other joining their ranks?), or are needed to stabilize the universe somehow, using the majority of their power to do so. That's probably enough random thought and theory spewing for one post though.

If you haven't you should definitely read His Master's Voice from Lem. I think he offers an interesting alternative. In his version, the ETI is (probably) not intelligent, it is not even an entity per se, it is more of a signal that is hinted to be "injected" into the neutrino background noise during the big bang by the inhabitants of a previous universe (about whom absolutely nothing is revealed - so it kind of displaces the problem). During the novel it is speculated that the signal is permeating the entire universe and very very slightly shifts the subatomic stochastics towards the formation of complex molecules and ultimately life. The scientists in the novel accidentally find the signal and are able to extract a huge amount of data from it (some of which even leads to the construction of artifacts) but all their accomplishments are described by one of the team as (more or less quote) like a caveman finding the blueprint of a cathedral, carving the exact same thing he sees on the paper out of wood and believing he has understood the message of the architect. Maybe ETI is a signal like that, and the TITANs were basically like a punch card music player playing out the human genome. The result is structured and somehow hints at a systemand perhaps even a purpose but it is at the same time senseless and cacophonic (as music).

Well if you think of a comparison between humans and ants, perhaps it would be wiser to compare ETI to ants (and well, humans to humans) :D . They'we been around for longer than us, the will probably outlast us. They have a bigger population, in some cases even larger superstructures than us. They are able to notice us and our actions can trigger reactions on their part but they do not really consider us more than they consider a stone or spider. Do they notice us? Sure. They just don't care. They do not comprehend us, but they do not have to - comprehension is not part of their adaptive strategy. Sometimes ants cause fatailities or even large scale catastrophes (there was this case of fire ants causing a short circuit in the landing lights of an airfield several years ago). That does not mean they plan to and want to hurt us - we simply run afoul of them doing what they do to everything else. It is possible to notice humans, even react to them and be completely inconsiderate towards them at the same time. ETI (again, Lem! :) ) may simply be a colony of artificial organisms (or perhaps even natural creatures) that were left to evolve for billions of years. Maybe they notice us but the fact that we are intelligent creatures is ocmpletely irrelevant to them. They just go around building solar system sized fabrication units at the edge of the galaxy to produce more of themselves without even thinking about what they do. Perhaps the Exsurgent virus is something they evolved hundreds of millions of years ago and they use it when they are disturbed -and even attempts to communicate may qualify as disturbance. Maybe the TITANs just put their finger in the ant nest and got stung. Transhumanity still exists because the purpose of the "venom" is not to kill, but to make an immediate stimulus go away. Some (perhaps most) civilisations go extinct from it, others don't - the ants don't care, as long as they are left alone. It is hard to tell (for me) which is more frightening: something actively malicious, that has a sinister plan with humans, or something faceless and uncaring. I tend to side with the latter usually. Even if you are destined to be eradicated, there is some solace in the feeling that you were somehow special, something worth the effort to destroy. Getting smashed the same way a deer gets hit by a 18 wheeler on the highway, accidentally, without purpose is much more depressing I think.