Who is Nestor in the novel, The Eagle’s Gift?

Nestor is an apprentice of the sorcerer Don Genaro, the special student of Vicente Medrano, the group's expert in medicinal plants. Nestor and Lydia live as a couple without being one. In Mexico City, Nestor allows that author Carlos Castaneda might be merely an "unwilling envoy" leading them to destruction, rather than Silvio Manuel's willing assistant. He sees it as possible to cross parallel lines by one's own power or under another's, and believes that Silvio frightens the apprentices so badly in forcing them to cross over that they are unable to recall the incident. They must now cross over on their own, but Carlos is thwarting them.