In this fanfiction, Harry Potter is likely to be a central figure, but he may not be the only focus. There could be a new generation of wizards and witches who are disillusioned with the current state of the wizarding world. These young characters could band together and start to form an empire. Maybe there's a character who has a deep understanding of ancient magic and uses it to gain followers. Another character could be a great strategist, plotting the expansion of the empire. And of course, there would be those who oppose this rise, creating conflict and drama throughout the story.
Most likely, Harry, Hermione, and Ron would be involved in some way. However, the fanfiction could introduce a whole new set of characters who are the driving force behind the empire's rise. These could be characters from different houses at Hogwarts who have united for a common cause, or perhaps characters from outside the school entirely. They could have unique magical abilities or knowledge that gives them the power to build an empire. And there may be antagonists among them as well, those who seek power for their own selfish reasons rather than the good of the wizarding community.