(the brotherhood outcast's were formed from brotherhood members who believed that the brotherhood of steel chapter in the capital wasteland lost focus of their original goal. To preserve and guard dangerous tech. From this the outcast were formed keeping the same goal of guarding technology. You find there base, a small building for independence. Member See's you. From there large dark power armor they say:)

"Hi wanderer. What are ya doing here? Wanna join, or just here to raid us?"