Storms, swords, and spying in the Sun books
Our protagonist says, on page 98 of In Green’s Jungles: “There is no such thing as magic, in the way you mean it. Things we don’t understand, ghosts and sudden storms for instance, make us think there might be. But ghosts are merely the spirits of the dead, and though I don’t know what causes sudden storms, I know they aren’t raised by magic.”
In Urth of the New Sun Severian accidentally conjures a storm up just by being angry. And in the New Sun books, aquastors, ghosts raised by technology, appear several times.
On page 103, describing Horn’s recovery of the sword one of the Vanished People had given him: “A full day after that [...] when something moved in the bone-littered filth of the river bottom, I jerked my hand away, sure that it was a venomous worm [...] then I saw the pommel, and saw too that the sword was struggling to reach my hand; and stretching my arm down I held my breath, but could not keep my eyes open in that vile water, and groped blindly for the grip that was groping blindly for me. And at last I closed my hand about it and felt it grasp me from within.”
In Shadow of the Torturer (page 91 of the Orb Shadow & Claw), Severian grasps his sword for the first time: “I clasped Terminus Est as I had the false sword at my elevation, and lifted her above my head, taking care not to strike the ceiling. She shifted as though I wrestled a serpent.”
Also, Horn/Silk seems certain at one point that the “devils” of the Whorl were inhumu, though supposedly devils live in Mainframe (where the gods hunt and kill them). If devils are rogue computer programs, it’s possible that they could communicate with people through glasses, and do their bidding. It’s likely that the black mechanics would know of them.
And I realized on my re-re-read of Long Sun that working glasses aren’t all that uncommon. All the rich and powerful of Viron seem to have at least one, as do some people who are neither, like Auk and Maytera Rose. And it seems that glasses can be used to communicate among cities - I think General Siyuf uses one at Ermine’s to contact Trivigaunte. Given that, there really ought to be a lot more contact between the cities than is evident in the books.
Furthermore, it ought to be possible for someone in one city to spy on a city across the Whorl using a good telescope. (Not directly across, because of the sun, but say 120° around the circle.) If you had a spy or ally in such a city take one of the eyes through which the monitors watch things, fix a telescope to it, and point it at your own city, you could then use a glass to watch your city from above, which ought to be pretty useful if you’re worried about being invaded.
And glasses are portable! There’s one in the Trivigaunti airship! They must be networked wirelessly. Being able to check out enemy troop movements from above is such a useful thing that somebody must have tried this.