Sister

 is a man found in Rivet City. He is an unapologetic Slaver, and, at Eulogy Jones' request, is in the city to capture an escaped android. In his room is a recording pertaining to the quest The Replicated Man, concerning the Slavers' desire to enslave some androids. However, Sister has grown to like living in Rivet City, for which he has abandoned this mission indefinitely.

Conversation with him is less than verbose: he has a simple goal and wants to discuss nothing but that. If asked about his name, Sister will refuse to go into further detail.

Unmarked quest: Slave Hunt
When you first meet Mei Wong she seems very scared because she is afraid of Sister. You can help either Mei Wong or the slaver and receive good or bad Karma based on your actions.

Glitches

 * If you agree to help Mei Wong but just randomly go and tear Sister's head off, there is a chance you will get no karma (or lose it) and talk to Mei, and the only things she will say will either be "Thank God he's dead" or "I wanna be alone right now".

Appearances
only appears in Fallout 3.