Well then, how's about this (abandon all hope of rational speculation first, as this is a wild, completely uncalled for speculative thought I had):
The underground movement, searching for places where they can meet and avoid detection, conquers their fears and begins meeting in the focus circles at night, reasoning that most other townspeople shun the places as haunted (can't remember if the focus circles are considered warded by the compact; if so, the madness attendant to trespassing might be a problem here!). Among the first circle to be chosen in this fashion is the one outside Jaelot.
Meanwhile, the cave on the isle in the Cildein where Ciladis sleeps, guarded by Riathan Paravians (and possibly others; we've only seen/read about unicorns thusfar) actually houses advanced but currently dormant computer technology, the primary purpose of which is to monitor and defend Athera. The Fellowship, of course, was unaware of it because the location is warded by the Paravians (extending possibly back to the drakes). Ciladis, therefore, discovered not only the Paravians but also this technology, which supposedly is in violation of the compact, and so had to be taken out of the equation, at least until the time is right.
Arithon's current day crew on board Khetienne (built by Riverton's master shipwright under Arithon's supervision in Merior, she OF COURSE is still seaworthy 200 years later
) discovers the isle. The Paravians withdraw before detection, taking Ciladis with them and allow the Khetienne's crew to discover the cave. Investigating, they inadvertantly activate the computer's directive. Halfway across the world, a portal opens within the Jaelot focus circle (sorry, don't have the book with me to give it it's correct name), revealing yet another computer bank, networked to the first. The focus circles, it turns out, do more than focus Athera's lane energies. The clansmen out in the Cildein and the underground outside Jaelot find they can communicate with each other, establish an accord of sorts opposing the light (not exactly an open alliance, mind you, but a sort of pact of non-hostility), then set out to make contact with the other focus circles.....