Organized and led by Brain, the Renewal Cult is an organization for ghouls who are working together towards gaining access to Vault City's medical facilities and know-how in order to restore their bodies to a proper human state ("renew" in the cult's parlance). They are a semi-secret organization, known to those who have a stake in establishing relations with VC and mostly ignored by those who have accepted their fate.
↑Fallout Bible 5: "59c. The other question was about renewing. I had always killed the rat God before I got to necropolis. Now I know (as of about 3 days ago actually) that renewing was the term the ghouls used for becoming truly human again. (I had just asked what it was before and what the heck the ghouls meant.) Any further info on renewing would be much apreciated. (though I don't expect you to explain how to actually do it or anything it remained pretty vauge in fallout2 and I just couldn't find a way to get it to happen. Everytime I tried to optimise the plant Vault city would wipe out the ghouls. Was it actually doable or just a clever ruse from the brain to take over the world? (he never did in my games and i didn't have to do anything to stop him, like in the cartoon his plans fall apart on their own I suppose) Thanks for your time once again. It was not possible for the ghouls to "renew" in Fallout 2 - it was part of the Brain's plans to get them human again (under his control). It is possible to save Gecko and VC - one of the walkthroughs on the Fallout fan sites should have info on it. And here's what the Brain specifically has to say about Renewal:
The Brain: Well as part of my plan to rule the world I intend to reward my Ghoul followers by finding a way to restore their humanity.
Chosen One: How are you going to do that?
The Brain: When I unite Gecko and Vault City under my rulership I will dedicate Vault City's medical labs to finding a way to reverse the effects of radiation that turned the people into Ghouls. They will be renewed, reborn, as humans once again.
The Brain: In order to take over the world I have to make sure that there's something worth taking over. I need to build a strong powerbase using Gecko and Vault City.
Chosen One: A rat plotting to take over the world?
The Brain: Well, despite your feelings about a rodent ruling the world; the actions I propose would benefit thousands of Vault City and Gecko's citizens. You may not care for me or my motives but the results are still well worth working towards.
Also, according to designer Matt Norton, "renew" was also a reference to the movie (and book) 'Logan's Run.'"