Emissary (noun)

1. A person sent on a mission, especially a diplomatic one.
2. A representative or messenger of a group or organization.

Origin:

From middle english emissarie, from old french emissaire, from latin emissarius, from emittere "to send out".

Examples:

1. The emissary was sent to negotiate a peace treaty.
2. He was appointed as an emissary to the United Nations.
3. The company sent an emissary to the trade show to promote their new product.
4. The emissary was sent to deliver a message to the enemy camp.
5. The political emissary was sent to broker a deal between the two countries.