Cerberus is the Mister Gusty robot that patrols the Underworld. If the player speaks to him he reveals that he despises the Ghouls, stating, "Personally I think they're a bunch of rotting zombie-maggot farms, and I'd sent them back to Hell if I could, damn this Combat Inhibitor!"
If the player has the Robotics Expert Perk, they can remove his Combat Inhibitor, sending him on a Ghoul killing-spree. He becomes immediately hostile to anyone. Usually he will kill everyone in the Underworld unless they are helped by the player. Removing the Combat Inhibitor results in negative karma.