The Condroni are passive observers, watching the environment but rarely interacting with it. ther effects on their environment, the distortion of radio-waves and the neurological damage to Sensitives, are both passive effects, the Condroni does not do it, and may or may not even be aware that this is happening.

I theorize that, in fact, these are both extensions of their observation behavior.

Their alterations to the radio waves are side effects of them listening in on it. This is would make sense in that every Condroni in a swarm affects only a certain band of radio waves. In the olden days, when radio surveillance was done by humans instead of algorithms, common practice would be for them to work in teams, each ember assigned to a specific band. The nature of the alterations, changes to dialogue and imagery instead of just adding static, implies that the Condroni has at least some understanding of it, even if only limited. It can tell the words form the background noise, is what I am saying.

The neurological effects may be a side effect of this, perhaps some attempt at mind-reading. Possibility a) is that the Condroni is only interested in sensitives brains, and so only harvests from them. possibility b) is more sinister, and is that the Condroni reads the minds of everyone in the field of effect, and the sensitives are simply affected differently, perhaps as some kind of allergic reaction.

Perhaps they have some other, further means of surveillance. Perhaps based upon sound or some medium unknown to science.

Why? Why are they doing this?

What is interesting about them is that, to whit, "The condroni and the ladroni are the only two strangers which appear in 100% of infestations. Thus, when there are no valid structures of suitable height, stranger infestations cannot occur."

So, we know that the Condroni is passively collecting information about the cities it forms in, and that other than the ladroni, the other Strangers either cant or wont spawn. My guess?

The Condroni's role in the Stranger infestations is in scouting out spawn-points.

the timeline passingly mentioned 'Super-Signal carriers' sustaining the rest of the strangers even after humanity is extinct. Perhaps the Condroni or some variant on the template?

My guess is that the 'Signal' is communication between the Condroni and other Strangers, telling them the lay of the land so that they know where and in what quantity to spawn.

More of a stretch, but this may have something to do with the Extrusion process, of whitch we still know little. My guess is that part of the extrusion process involves the Condroni signals, either by manipulation the Condroni, either through trickery or the 'Callyphanx' mentioned in the timeline, to send out false signals to the Strangers to make them spawn on command in specific locations. Their inertness is a side-effect of them spawning where they should not.

Perhaps later in the timeline, humanity discoveres a way to spoof the Condroni signals directly with machines.

Thoughts?