As the leader of your empire, you must collect coins, to move troops, upgrade your provinces, and pay the loyalty of your generals. If your money reaches zero. YOU LOSE
All of this with the goal of expanding your provinces while maintaining the support of your fellow citizens, who will either lose or gain faith in your leadership through your actions. Coins come from the citizens of the region. The happier they are, the more coins they will produce.
You will also recruit soldiers from the regions, or you can hire artists and magistrates who modify the support of the citizens of the region. Obviously, this will cost you money each turn.
The further the province is from the center of the empire, the less support they will give you. You may reach a point so far away that the provinces are always on the verge of rebellion, no matter what you do.
If the support of the citizens of a region were to reach zero, the region would rebel and stop giving you money and recruits. You would have to punish it and make the rebels pay for it. If all your citizens stop supporting you. YOU LOSE.
Generals will gain prestige among the people with each victory, and at some point they will demand payment to feel satisfied under your command. If you do not pay them, they will turn against you and try to reach the capital to seize power. If a general rebels and conquers the capital. YOU LOSE.
But the "barbarian" regions do not stand still, they develop and accumulate soldiers every turn, making it cost you more soldiers and money to conquer them. If your legion loses a battle, you may pay a ransom or dead. YOU LOSE
It is possible that some regions develop so much that they become an empire that expands into their vicinity and challenges your power. These empires can take provinces from you, and even conquer your homeland and destroy your imperialist dreams. If a rival empire conquers the capital. YOU LOSE
Always keep in mind the time limit of your own life. Death reaches us all. If you reach the turn limit, you die of old age. YOU LOSE
Only by conquering the entire map do YOU WIN and you will be remembered for centuries as the conqueror
