Requires Paper to be used and only once the unit as been expended for influence in a city state it is possible to build another one.
The Emissary is the first diplomatic unit available to a player, and represents the early attempts at peaceful cooperation between civilizations. As the culture of diplomacy is, in the Ancient Era, still quite crude, the Emissary is not terribly effective. Earning only around 20 from a Diplomatic Mission, the Emissary has not yet mastered the art of statecraft, nor, unsurprisingly, the foreign languages of neighbouring city-states.
Though the cheapest and earliest-available diplomatic unit, Emissaries are not terribly reliable as a source of steady Influence. Players should only use Emissaries to secure or maintain relations with a city-state you are already friendly or allied with. As such, it is best to use these units simply to augment your efforts to fulfill city-state quests.