Join the beta test before the update launch.
To try the BETA, please follow these steps:
Open Steam
Right-click on Age of History 3 in your library
Select Properties
Go to the BETAS tab
From the "Beta participation" drop-down list, choose "betatests"
Wait for the game files to update. If nothing happens, restart the Steam client
Launch the game
Unions
New diplomacy option: Form Union
If a union proposal is accepted, the Civilizations will merge into one.
Here you can see how it works:
New values for:
game/gameValues/GV_Diplomacy.json
DIPLOMACY_UNION_COST: 25,
MAX_UNIONS: 1,
Have fun!