If a Civilization sends enough 
Envoys to a City-State, the city-state will declare that civilization as their Suzerain. Each city-state will have no more than one suzerain at a time. Each city-state has a unique icon and Suzerain bonus.
- → See City-States for information on unique bonuses obtained when becoming the Suzerain for any given City-State.
Suzerain Requirements
- Send at least 3 Envoys to the city-state.
- Have sent more
Envoys to that city-state than every other Civilization.
Diplomatic Bonuses
- The city-state follows you into war and peace with other players.
- Your units may enter city-state lands.
- Your Builder units may improve city-state tiles.
- See 3 tiles around the city-state.
- Can pay Gold to temporarily take control of the city-state's military.
- Gain ownership of all the city-state's resources.
