Ruby is a prostitute born in Carbon and the first to greet the player character on arrival.
She is available for sexual encounters (for 10 caps) and asks the player to help her find her cat, Mr. Pussy. Mr. Pussy can be found, however he will be found dead, having been killed by monsters in the Crater. You can bring his corpse back to Ruby for caps and XP.
Later in the game, her locket is stolen by raiders attacking the town. Ruby asks the player to retrieve it during his attack on the raiders' base, the Mill. She claims to know Harold who traveled through the town some time ago.
Ruby also gives you the quest kill drunken raiders, where you have to kill 10 raiders in the Carbon Bar.
Depending on gender and if you're Cain, she will give a different speech after paying for her services, and she will vomit. She must be informed that he is a ghoul for her to understand it, but telling her this will not prevent you from further wasting money on her services.