Warning: the following contains spoilers for the following works:
The Expanse, S01E01-S03E10.
Abaddon's Gate (Book 3), James S.A. Corey
Three-Body Problem &The Dark Forest, Cixin Liu
If you want to try it out, read 5 books and watch almost three seasons of television.
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!!The ring gates are a Dark Forest weapons system. If this was clear to others, and I'm catching up, well, I'm slow. But, I just found out about Brin (1983).!!
Then, I got it. It's such a well-structured Whatsit.
I feel pretty good about this realization. I'm glad that these works work so well together.
I think the protomolecule was sent on Phoebe and got trapped by Saturn