Now you can reach Expansion Victory when your country grows big enough and you reach high nobility titles.
Getting Started
You man contact in terms of noble affairs is naturally Vertuttiy the Old Herald. He made you a noble as a part of tutorial and now you can talk to him if you want to improve your noble title and reach Expansion Victory.
There are 17 noble titles with first two being Commoner and Noble and last one is God-Emperor (or Goddess-Empress), each of those above Commoner have different requirements, but in order to avoid spoilers, just talk to Herald and he will fill you in.
New Quests and Location
The Expansion Victory adds 4 new quests and 1 new quest location that is opened at later stages of your victory progress. As always, there are multiple solutions to the tasks you may be facing when progressing the victory, so don't feel yourself locked when something looks inaccessible at your stage of the game.
The Expansion Victory in theory is made technically achievable at any point, so you don't need to create new heroes, although doing it with the fresh hero would probably be the smoothest experience. Whether you will be able to fulfill all of the requirements with your specific hero is another question.