runsforcelery wrote:
What makes you think he didn't do exactly that?
It would have been the obvious question, but there is really not much value in the answer after 800 odd years. Any group that was planted needed to stay secret, and the events of the next hundred years would only demonstrate the need to really stay hidden. Even if Merlin could locate one of these groups, at the time he would not have been able to do much: "Just popping in to say hi, and I know about you secrets." would likely not get very far. He has to vet anybody he shares his knowledge with very carefully.
As others have pointed out, it is a matter of priorities, and there is not a lot that another secret group could do for him, unless it was exceptionally well placed and capable (and he can trust it).