Resonance. [It's a simple, almost bland word with a whole ship's worth of baggage.]

In this world, very few humans seem to posses it. It would appear that our individual alignments to these Arehtei beings may serve as a sort of replacement to resonance, yet the locals don't seem to be aligned to any Arehtei at all. [Except maybe Simpathis? It's a little unclear- he needs to do more research into that.] Effectively, that would mean none of the locals can see or hear us.