The Diplomat is a unit that specializes in Diplomacy.
That being said, they have a couple nifty abilities.
If your diplomat is in the domain of a player owned city, and that city is unhappy (-600), you can FUND THE REBELS! Causing an instant rebellion, for a princely sum of gold.
If your diplomat is in a neutral city, you gain +200 relationship with that city, and you can Fund their defenses so they make more units to defend themselves for yet another princely sum of gold.
Now in combat, the diplomat doesn’t have much, however, he has inspiring aura, inspire, and bribe. Bribe works like convert, except it costs gold and rolls against physical rather than spirit, and the control cannot be broken. Inspire increases the damage of a single unit by 3 for one turn and prevents them from having range dropoff, like a longbow. Inspire has no cd, and is the main method for diplomats to gain exp. Out of combat, the diplomat buffs your armies with promises of good cheer and comfort, increasing the upkeep of all soldiers by 2 in the army it is in, but also boosting their out of combat morale by +500.
The diplomat is a t3 irregular with forest concealment, urban concealment, low hp, low res and low def. Keep him safe!