He told them
"Why can't they figure it out on their own? What about the black librarian? Isn't she powerful?" Eddie was still unconvinced. He thought that there was more to it than just getting rid of the anti-government influence.
If the underworld was as Dunn described it. Why would they need Ryan's help figuring out puppets lurking amongst their subordinates? It doesn't make sense.
"Indeed, figuring out the puppets within is easy and doesn't require using my ability to discover their identities. There are obvious symptoms, and their survivability on drugs is one glaring factor."
"Then why?"
"The seer made it so they would never know. They could never take the initiative to know. Unless a puppet was to stand in front of them and state his identity, they would never know."
"Blood contract?"
"Yes, the seer would have never simply trusted them if not for it."