What Atom Requires DLC, Far Harbor Quest
This quest will be triggered or can be aquired when you complete Visions in the Fog quest.
Related points of interest
Stages of "What Atom Requires" quest
1. Help the Children of Atom
I've joined the Children of Atom. If I want to really earn a place for myself in this family, it'd probably be worth asking around to see if anyone could use my help.
1.1. (Optional) Show the Icon to the High Confessor
1.2. (Optional) Assist the Grand Zealot
1.3. (Optional) Help the High Confessor
1.4. (Optional) Help Zealot Ware
Next / new quests are The Heretic (DLC, Far Harbor), Witch Hunt (DLC, Far Harbor).