"Civ 6 Rise and Fall Governors
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You'll be familiar with this concept if you've ever played an Endless game - Civ VI is getting Governors. These are special characters who can be assigned to cities (they don't exist on the world map) to give them powerful bonuses according to their unique promotion trees.
Strenger says there will be seven different types of Governor, inspired by historical archetypes, and you can only have one of each. You can spend a Governor Title to either recruit a new one, or promote an existing one, so there's a nice wide/tall trade-off there. Governor Titles are "primarily" unlocked through the Civics tree, but Strenger's use of that word hints that there will be other sources - perhaps a leader or a civ's unique ability?
Here are all the Governors we know of right now:
Liang, the Surveyor: grants builders extra charges, but some of her later promotions can unlock improvements - the City Park and the Fishery - that can't be built any other way.
Raina, the Financier: one of her later promotions enables you to purchase city districts with gold, like you can with buildings and units.
Amani, the Diplomat: exerts Loyalty pressure on nearby rival cities each turn, increasing the chance they'll declare indpendence and, if already independent, increasing the chance they'll join your own civ. You can even put her in a city-state, where she'll act as an envoy on top of these effects.
The Cardinal: mentioned by Eurogamer, this is quite clearly a religious Governor, but we don't know anything about their abilities just yet.
It sounds like there will be a military Governor who can "be a saviour during a city siege, and can make or break a city's defence against a powerful attacking army," according to this blog post from Firaxis.
All Governors will also bolster a city's Loyalty, so wide players will probably want to recruit many rather than promote a few, and send them around their empire keeping the people in line. Governors have five promotions each."