Well, it could be a very dark plot. Maybe Harry is under some dark magic influence that makes him lose his mind and start killing. It would completely change his character from the original story.
Perhaps in this fanfiction, there is some kind of misinformation or false accusation that drives Harry to the edge. He might be framed for something he didn't do, and in his desperation to clear his name, he accidentally kills someone and then spirals out of control. This would create a very complex and tragic storyline.
In the 'harry potter becomes a murderer' fanfiction, it could be that he is forced to kill due to a threat to his friends or Hogwarts. He might think that sacrificing a few lives by his own hands is the only way to save the many. But this act of killing then corrupts him, leading him down a very different path from the heroic one we know. It would be a huge departure from the traditional Potter narrative and would likely explore themes of morality, corruption, and the consequences of extreme actions.
If Harry Potter becomes an obscurial in fanfiction, the story could take a very different turn. He might not be as eager to attend Hogwarts as he was originally. The Dursleys might have an even worse time with him because his obscurial powers could lash out. At Hogwarts, teachers would be extremely concerned. Snape, for instance, might be even more critical of him, seeing him as a potential danger. And Harry would have to learn to control this new and dangerous aspect of himself.
The perception of Harry would be turned upside down. In the original series, he is the symbol of good and the one who defeats Voldemort. But in this fanfiction, he is the one causing harm, which makes readers question everything they thought they knew about his character. His motives, actions, and relationships would all be seen in a new and disturbing light.
In such a fanfiction, Harry might gain the ability to rise from ashes, literally and metaphorically. He could have the power of regeneration and immortality like a Phoenix. This would change his battles, for example, he could fearlessly face Voldemort as he could always come back even if defeated. His relationship with his friends might also change. They would see him as an even more extraordinary being, and he might have to deal with their awe and a bit of distance that could come from his new form.
Well, if Harry Potter becomes a villain in fanfiction, it would be a complete subversion of the original story. He might use his powerful magic skills to dominate Hogwarts instead of protecting it. He could form alliances with the dark forces that he once fought against. Maybe he would start to spread fear among the students and teachers, and turn the school into a place full of chaos and tyranny.
Well, it could be really interesting. Harry Potter, with his magical background from Hogwarts, would find the world of Witchers quite fascinating. He might be intrigued by the Witchers' potions and their unique way of fighting monsters. Maybe he'd try to combine some of his spells with the Witchers' combat skills. For example, he could use a Patronus charm while also slashing at a monster with a Witcher's sword. And he'd surely be interested in the different kinds of monsters in the Witcher world compared to the ones he faced in the wizarding world.
The plot would become very dark. Harry would no longer be the hero, so the fight against Voldemort would likely take a different turn. Maybe Voldemort would see Harry as an ally instead of an enemy. The other characters would have to either try to change Harry back or find a new way to defeat Voldemort without Harry's help.
In a 'Harry becomes Sauron' fanfiction, it might start with Harry being disillusioned with the wizarding world. He discovers some ancient magic that has a connection to Sauron's power. As he delves deeper, he becomes influenced by Sauron's will. He could then try to reshape the wizarding world in his image, which is now a dark and tyrannical one. He might even try to bring Middle - earth and the wizarding world together under his rule.
If Harry Potter becomes a demon in fanfiction, his relationships would be severely affected. His friends like Ron and Hermione would be very confused and possibly afraid of him. They might try to find a way to reverse the transformation. And Hogwarts itself would be in chaos. The teachers would be divided on how to deal with him, some might want to help him while others might see him as a threat to the safety of the school.
Well, it would be a total chaos. He might use his magic skills to cause destruction. For example, he could turn Hogwarts into a dark fortress and rule over it with an iron fist. His friends would be shocked and probably try to stop him, leading to some really intense battles.
It would probably include Harry's initial confusion when he first encounters Eevee. He might be used to magical creatures in his own world, but Eevee is something entirely new. There could be a lot of descriptions of Eevee's appearance, like its fluffy fur and big, innocent eyes.