Motor-Runner

Motor-Runner is the leader of the Fiends, located in Vault 3

Background
Ranger Bryce Anders remarks that Motor-Runner has survived several previous NCR assassination attempts, which prompted Colonel Hsu to give Anders the mission of killing the Fiend leader personally. According to Hsu, Motor-Runner has a habit of decapitating dead NCR troopers.

Motor-Runner regularly purchases slaves, and has done business with Dermot and Saint James on at least two occasions. He is found in his throne room in the Vault 3 maintenance wing flanked by his two guard dogs, BoneGnash and GhashBone.

Quests

 * Aba Daba Honeymoon: Diane gives the Courier the quest to deliver some drugs to Motor-Runner.
 * Bounty Killer: The Courier is ordered by James Hsu or Bryce Anders to kill Motor-Runner.

Other interactions
The Courier can sell him various drugs (Jet, Psycho, Buffout) for 20 caps (or 22 caps, if the player passes the Barter check) if passing a Speech check at the entrance of Vault 3 when speaking to the Fiend at the door. 22 caps are more than the player character will ever be able to receive from selling drugs valued at 20, with the exception of one instance involving Ricky.

Appearances
Motor-Runner appears only

Behind the scenes
Motor Runner is the Four of Spades in the deck of Vault playing cards included with the Collector's Edition of Fallout: New Vegas.

Bugs

 * If you have completed Still in the Dark, Motor-Runner will talk in normal fiend dialogue after the initial forced talk, including, "House is dead, wonder if Motor-Runner will let us hit the Strip now."
 * There is a possible fix for this by engaging him in combat, running to the vault entrance, and then holstering your weapon. This will allow you to complete the quest.
 * When the Courier says they will tell the NCR he is dead, even if the Courier asks him to give them caps with a high Speech skill, he still rejects the offer.