There's a possibility that the main villain is a dark entity that has been awakened by some accident or dark magic experiment. This entity doesn't have a physical form like a human wizard, but it can possess other beings and use their powers for evil. The players would have to figure out how to exorcise this entity from the wizarding world and stop it from causing chaos and destruction.
It could be a long - lost relative of Voldemort, carrying on his dark legacy.
Maybe a new character, a Muggle - born who discovers they have a special ability that no one else has. This character would then be thrust into the wizarding world and have to navigate through Hogwarts while also being the key to solving a big mystery in the new game story. They would interact with the old characters' descendants and form new friendships and rivalries.
It could be a rogue Death Eater who escaped punishment and has been biding his time. He might have a new, more insidious plan to bring back the dark ways of Voldemort.
A possible main villain could be an ancient sorcerer from the new dimension who has been awakened from a long slumber. He's enraged that the wizarding world has been interfering with his dimension's magic, and decides to take revenge on Harry Potter's world. He has powers that are unknown to the normal wizarding world, like the ability to control time in his dimension, which makes him a formidable foe.
Perhaps a new student from a far - off land could be the main character. This student could bring new magical traditions and knowledge to Hogwarts, and have to deal with the cultural differences while also getting involved in some big adventure, like unravelling a mystery that threatens the entire wizarding community.
It could be a new character created by the fanfiction author. Maybe a powerful wizard who was once shunned by the wizarding community and now wants revenge by stealing magic.
A dark wizard who has merged the dark arts with Wonderland's magic could be the main villain. He might have created some sort of dark Wonderland where all the creatures are under his control, and Harry has to break this control to restore balance.
It could be a powerful veela who has a grudge against Hogwarts. Maybe a Hogwarts student in the past wronged her family. She uses her charm and powerful magic to try and bring chaos to the school. She first lures some of the male students with her beauty and then uses them to carry out her devious plans. For example, she might make them steal important magical artifacts from the school that are used to keep Hogwarts safe.
The new story might revolve around exploring new parts of the wizarding world that were previously unknown. For example, a hidden magical realm that has a connection to Hogwarts. The game could have the player, as a new student, discover this realm and figure out how to stop the dark forces emerging from it. They would learn new spells and make new friends along the way to help them in their quest.
The new story could center around a new dark wizard threat. The game could let players be part of the fight against this threat, teaming up with familiar characters like Harry, Hermione, and Ron. They might have to solve complex puzzles and use new spells to defeat the enemy. For example, the dark wizard could be trying to steal powerful artifacts from Hogwarts, and the players' task is to stop him. This would involve exploring different areas of the wizarding world, from the Forbidden Forest to Diagon Alley.
Perhaps the main villain is actually a corrupted version of a well - known character. For example, if Hermione was somehow influenced by the dark magic associated with the runestone path and turned against Harry. It would be a very unexpected and heart - wrenching twist, as she has always been such a loyal friend. But the power of the runestone path could be so strong that it changes her fundamental nature.