The Undead Conquerors are a group of slavers that are made up of Ghouls, normal and feral. It was founded in the year 2286 by Julian "Flame" Viel, a Legion Centurion who had partially turned into a Marked man before finding shelter in a cave to hide from the harshness of the Divide. After the conclusion of The Lonesome Road dlc of Fallout: New Vegas, Flame, with his damaged centurion armor and marked beast eyes helmet, managed to find the exit of the divide and flee from the irradiated area moving east because he knew that if he went back to Caesar in the state he was in, he would either be killed or crucified. So with the faith and belief he still holds from the legion, he traveled east until he made his way to Missouri and took notice of the amount of Ghouls in the area, both feral and non-feral. Gaining an idea on how he can continue Caesars belief, he convinced the Ghouls that were treated poorly by the humans into joining his group which soon turned into The Undead Conquerors.

In the beginning years of his faction, they would enslave some people that were unfortunate enough to run across them and would capture feral ghouls to be used as dogs for their army. In the year 2288, Flame would come up with an idea that would not only help them grow in numbers, but would also be a mark on how infamous they are. He would hold a trial by duel and would force his slaves to fight to see who would be worthy. And if the victor has been determined, Flame would force the slave over to his "ritual room" filled with radioactive material that would force them into becoming a ghoul. If the slave tries to resist, Flame would threaten that he would give him an incredibly slow and painful death if they did not comply.

Their main camp is located by the Mark Twain lake with outposts located around the lake and are at war with The Missouri Rangers for control of the land. When asked about the war between the two, Flame would point out that it reminded him about the war between Caesar's Legion and the NCR back west, finding it ironic how it never seemed to leave him alone since his departure of the Divide. They are an open faction for the player to join, but would either have to become a ghoul themselves or have a high enough speech to convince him to remain human.