Emissary

From publisher blurb:

In some regions, complex organizations - such as secretive guilds or branches of the governing body - control these spies and regulators, but in other lands the authorities hire freelancers. Most often, however, the rulers of kingdoms and empires rely on a small number of discrete operatives whom they can trust. And few are as competent as the Emissary. This four page Prestige Class PDF is an easy-to-integrate PC class and just the sort of thing needed for DMs to add depth to any great d20 fantasy campaign world and gaming session.