The Dandy is one of the many generic archetypes introduced in the Advanced Player's Guide, available to anyone with Diplomacy. You lean the ins of smooth-talking to get by the social encounter. You start by numbing up your Deception and Society skills and spend downtime to manipulate the locale rumors. Other feats include Covering for That Guy when they do something stupid (it has a 10 min cooldown so...); You can recall Knowledge on any topic (hairstylists are well versed in demon politics?); Can use deception as a job, and get your party into parties.
Dandies Are a good thing to have if your doing a campaign with many social encounters, especially if every other PC is dirty murder hobos or the recurring villain is a snob.