The City was the name of a loose organization of ultra-powerful "winners" of The BackHalls who came together to protect creatures in the halls that were innocent or truly lost, typically in the form of any children who found themselves in the halls due to magical malpractice.
Guidance Counselors
The guards and warriors of the city who dedicated their eternal trapped lives to protecting the city and the creatures within called themselves Guidance Counselors. Only a Guidance Counselor could deem another creature worthy of entering or living in the city.
Typically to become a Guidance Counselor, one needs to have defeated and absorbed every "Master" of the halls, effectively having "beat the game".