The entire book could be considered one. But some points stick out.
- The central premise of the book is as existential as horror gets. Self-awareness was an absurd evolutionary fluke. We’re about to be out-competed by our own natural predators, hyper-logical A.I.s, and aliens who don’t waste precious processing cycles thinking about themselves. Oh, and human psychopaths aren’t aberrations, they’re an evolutionary preview of humans evolving away from sentience again. And we only catch the stupid ones - the smart ones blend in perfectly despite being non-sentient.
- Imagine you're Amanda Bates. Before Theseus you were quelling a terrorist group on Earth. You caught 4 terrorists and let your soldiers do anything with three of them. Then you locked the soldiers up. Then you told the one surviving terrorist what happened, gave her a microwave gun and sixty seconds alone with the people who just killed her comrades-in-arms, after which time the two of you will sit down and have a nice chat. Cold? I say freezing.
- Siri's journey home. On the occasions he wakes up he notices transmissions from ships who sound like they're fleeing the solar system before getting cut off abruptly. Channels which once played human music have been replaced with droning filled with vampires' vocal clicks and pops. After all, what did we expect to happen after the human race resurrected its only natural predator, engineered away their only weakness, then started emigrating to digital "Heaven" en masse leaving our bodies as pre-packed meals? It was only a chance mutation that cheated vampires out of their natural position as apex predator, and it's strongly implied they've just inherited their birthright.
- There's no FTL in this 'verse. That means two options: either Rorschach just happened to be listening during the 21st century and lives within a ridiculously small radius of Earth; or there are millions of these things, scattered across the galaxy to lie in wait until a star system shows signs of containing a threat.
- The crew hypothesizes that Rorschach is a "seed," like that of a dandelion, carrying the implication that the "species" (if you can even call it that) lives around and in sub-brown dwarfs like Big Ben and sends seeds out to new subdwarfs, eventually covering immense tracts of space. Rorschach is also still growing, and it's suggested that this incomprehensible cosmic monstrosity is still a baby.
- Everything about Rorschach is on some level frightening. The artifact itself is described as resembling a city-sized crown of thorns, constantly arcing lightning and dimly illuminated by the red glow of the failed star it orbits. Its electromagnetic field induces paranoia and hallucinations in humans who try to explore its cavernous tunnels. And although the contact team's linguist is thoroughly convinced it's non-sentient, and therefore can't really "want" or "feel" anything, Rorschach nonetheless manages a terrifyingly good impression of rage and spite in issuing death threats to the crew.
