Hi, Chevy. I don't think I've formally introduced myself yet. Fragments and Feedback is so full of new people now. It seems we haven't scared you off yet, so I'm going to give it a try.
You've presented me with a pretty good hook here. The best element of it is a sense of strangeness and of the unknown. There are things here that are taking a ride in people's minds and that's pretty neat. I want to know why and what they are, exactly, and those questions will keep me reading.
"As the beings moved closer to one another, the rider played along the margins of one of the minds, looking for gaps and loosened edges."
The term, "beings" confused me. I assumed, after reading the entire intro, that you meant humans, but maybe you don't. If you do, I think the more clarity you can provide in the opening sentence, the more of a hook it provides. Ironically, this is more true when your hook is veiled in mystery and shadow. Tell us what you know, what you can tell us and we'll want to know the rest.
" He'd always had a knack for riding, but more than the others, he knew how to feel a mind out and make an effective connection."
When you say, "but more than the others," what do you mean, exactly? I'm not sure if it's modifying the first part of the sentence or the last...as if his knack is more than the others or his ability to feel a mind out and make an effective connection is more than the others. I assume you mean other riders, but that's not clear either. In fact, if you don't mind my suggestion, I would cut out the middle part, use a semicolon to separate the two clauses, and call it good. If comparing him to others is truly important then there is plenty of time to do that.
" He found a spot now and insinuated himself in and around it."
Why "now?" It always sounds strange in past tense and in this case I don't think it's necessary.
" It was fascinating, but he could only see what the one he rode wished to see, never in control."
This seems like a strange time and way to say this. I guess I am looking for something the rider wants to see that he is being kept from seeing because he is not in ctonrol. As written, it feels a bit like a nonsequetor. Also, tacking "never in control." is not grammtically correct, I think. It's a phrase that doesn't really belong in this sentence.
All right, I'm done nitpicking. I'm going to read the other comments now.