So I have an idea, and one I'd like a little help with. This is in homebrew only because it conflicts with the established plot in the final chapter.
There were never any TITANs.
Of course there was a military project and machines like them were being developed, but ultimately the destruction of the Earth and the devastation of transhumanity's population came about at the hands of a hypercorp. The exsurgent virus was developed by a seed-AI, and any evidence of this is back on Earth where no one can get to it.
I'm not sure what to do with the Factors, but I think the seed-AI developed the Gates in order to spread itself throughout the galaxy. Which I suppose means it's not too different from ETI...except that we [i]made[/i] and now the rest of the galaxy will suffer for it.
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The end really is coming. What comes after that is anyone's guess.