From the publisher:

Negotiation can be more than just a skill. It can be an art.

For those that seek to earn their living or even change (manipulate?) the world through this art, the prestige class of Emissary is available.

An Emissary is the best ?front person? any group or organisation could hope to have. They might serve merchant traders, or at the front desk for banks or magic item stores, or as guild representatives, lawyers or even as ambassadors for entire kingdoms. Their ability to secure fair or even advantageous deals in the most disadvantageous and dangerous of circumstances makes them invaluable to any group.

There is a dark side to the art of diplomacy that no skilled Emissary can afford to ignore. Any Emissary trains in the skills needed for self defense, and not only against sword and bow, but also against knife and venom.