A Union is when two or more countries unite, and make a stronger one. You can find the "Union" in the diplomacy tab.
A Union is not a rare thing, but its not easy to do. You have to have a good relationship with the other one, and do other things in order to make a union. Here is what we know that can help you:
- Have at least 60+ relationships with the other. The more the better.
- Being in a war with a country that they hate can also help.
- You have to be patient. If you spam the Union, you will never unite with the other one.
That's all we know now. I hope it helped.