(Sniff, sniff) Hmmm, I smell the distinctive aroma of Cheezy Poofs on you. You don't happen to have some to spare do you? I just love Cheezy Poofs.
Brain is an intelligent albino mole rat with an enlarged braincase, the brother of Keeng Ra'at.
He is the unlikely leader of the renewal cult in the ghoul town of Gecko and seeks to take over the world. He lives in an underground cave adjacent to the Gecko nuclear reactor. He loves Cheezy Poofs, and will ask the player to give him some if the player has any in their inventory as he can smell them.
In the short term, he seeks to build an alliance between Gecko and Vault City based on power from Gecko being sent to Vault City in exchange for medical research on how to "restore" the ghouls to humanity. The cult is symbolized by the ankh, and its members wear ankh necklaces. The renewal cultists seek to "renew," i.e. become human again.