After accessing the facility beneath the manor, the player has to use the terminal to receive the Order of Mysteries - Rank: Initiate holotape. After listening to it, the player has to request a mentor assignment from the terminal, which will require them to travel to Lewisburg and find Mistress Natasha Hunt.
Lewisburg is located in the northeastern Ash Heap, directly southeast of the manor. It's a toxic area, so a repaired veil (using the fabricator in the facility,which grants the Veil of Secrets) will help protect against airborne diseases and damage.
Lewisburg is crawling with ghouls. After dispatching them, Mistress Hunt is found near the Nuka-Cola machine on the corner of W. Foster Street near the ice cream parlor. Her body contains a holotape and a login with password for the mainframe. The holotape will reveal that she came to Lewisburg to hunt raiders who were preying on the Order. To complete her assignment, find Kerry's body on top of the building opposite the one where Hunt was. Grab Kerry's Orders to complete the optional objective.
To continue the questline, the player has to promote themselves using Hunt's login details, then relog as themselves. Hunt's login grants access to the infirmary and council chamber terminals, as well as the ability to fabricate the Garb of Mysteries from the fabricator. The promotion starts the next part of the questline: Novice of Mysteries.
There is a bug when trying to turn in the final part of the quest. When you log back into your account on Cryptos for the promotion, spam your spacebar key on your keyboard or jump button on your controller to get around the bug. You'll be stuck on the final part otherwise.