Student or Learner
Can I use the expression: "descended into the underground" to describe someone who is hiding from the authorities?
As a true-crime book fan, i think that "descended into the underground" sounds more like the person actually ventured beneath street level (as if they were going to live in subway tunnels). Usually when someone assumes a new identity and lives in a "safehouse" to avoid being found we say that they "have gone underground" or that they "went underground."
Somebody who has descended into the underground may have taken a trip to Hades.