Driver Nephi can be found alongside six other Fiends in a burned-out building north of the Samson rock crushing plant, and south of the South Vegas ruins east entrance. He is nicknamed for the unique golf club he carries with him into battle, Nephi's golf driver.
Nephi is on Major Dhatri's hit list for the quest Three-Card Bounty. Dhatri states that 1st Recon had previously been sent to kill Nephi, but proved unsuccessful after multiple attempts, as Nephi tends to use his own men as meat-shields to protect himself, and is also tough enough to have managed to survive despite 1st Recon snipers having managed to land at least a couple confirmed shots on him.
Major Dhatri also warns that Nephi is exceptionally fast, having earned his nickname by managing to kill a dozen armed NCR troopers in melee combat before they even knew what hit them. In fact, he moves 25% faster than a normal human non-player character. Bert Gunnarsson will comment on Driver Nephi's passing after his death, but will not elaborate further on any prior relationship he had to Nephi or the Followers of the Apocalypse.
Like many Fiends, Nephi dabbles in the slave trade, and did business with Dermot and Saint James on at least one occasion. It was he that purchased the little girl and her family that went missing from Aerotech Office Park, giving 400 caps for the little girl's sister and 150 for her brother. He only paid 50 for the little girl, however, despite Dermot's best efforts to convince him to pay more and to wait until the girl got older.
Driver Nephi has an unused unique dialogue tree in the GECK, in which the player character can ask him basic questions about himself, his golf club, Violet, and Cook-Cook. This dialogue also reveals that Nephi is from Utah, and was once a friend of Bert Gunnarsson and a member of the Mormon Church before he fell under the influence of the Fiends and became Driver Nephi. It was also possible to inform Nephi that the Courier wanted to check on him on the behalf of Bert, in which Nephi stated he would never go back to the church.
Driver Nephi's name may be a reference to Nephi (pronounced /ˈniːfaɪ/) which are four sections of the Book of Mormon, the religious text read by the Church of Jesus Christ of Latter-Day Saints. Within this text are four individuals named Nephi as well. The city of Nephi, Utah is located south of Salt Lake City.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
Driver Nephi may have received his name because of his affiliation with the Mormons at New Canaan prior to becoming a Fiend (mentioned in the cut dialogue found in the GECK).
In dialogue with Major Dhatri, he says "let him get close and he'll take your head off" this is in reference to the Book of Mormon story where Nephi beheads Laban, an evil steward, although, in the Book of Mormon, Nephi does not wish to kill him.
End of information based on unverified behind the scenes information.