One idea could be that Harry discovers a dark secret about his family that leads him down a dark path. For example, he might find out that his ancestors were involved in some really evil magic and he starts to explore that side of magic. Another could be that the influence of Voldemort somehow remains and corrupts Harry's mind over time. Maybe the Horcrux inside him wasn't completely removed and it starts to change his way of thinking.
Well, obviously Harry himself is the central character. But aside from his friends, characters like Draco Malfoy could have a different relationship with Harry. Instead of being just a rival, he could be an ally of sorts in Harry's dark journey, or perhaps he tries to use Harry's newfound darkness for his own gain. Snape too could be important. Given his complex relationship with Harry, he might be in a position where he has to choose between helping Harry return to the light or letting him continue down the dark path.
In such a fanfiction, Harry Potter's transformation into a horse could be a part of a larger plot. For example, it could be related to a dark magic experiment that was meant for something else but accidentally affected Harry. His friends, like Hermione and Ron, would be in a frenzy trying to figure out how to turn him back. Hermione would likely be researching every book she could find on Transfiguration and dark magic. Ron, on the other hand, might be more focused on keeping Harry safe and comfortable in his new form. And Harry himself would be dealing with the shock and confusion of being a horse, all while still having his human mind intact and trying to communicate with his friends in whatever limited ways he can.
In some fanfiction, Harry Potter can be portrayed as 'dark' and a 'bearer' in very different interpretations from the original series. Fanfic authors often like to explore alternative character arcs and personalities.
He might start spending all his free time watching animations and collecting related merchandise. He could even try to use magic to create his own animated world.
Well, it could be really interesting. Maybe Harry would start to see the magical world through the lens of cartoon logic. He might use cartoon - like spells that have over - the - top effects. For example, instead of a normal Patronus charm, his Patronus could turn into a huge, colorful, and goofy - looking animal that acts like a cartoon character, bouncing around and making silly noises.
Well, he would lose his human form and all the abilities that come with it. He would have to learn to move and hunt as a basilisk, which would be a huge adjustment. His friends might not recognize him and could even be afraid of him.
In some fanfiction, it might be related to a hidden magic within Hogwarts itself. There could be a mysterious force in the school that reacts to Harry's unique connection to the place. For example, if he uncovers a long - forgotten chamber or artifact that has some sort of transformative power. Since basilisks are associated with the Chamber of Secrets, it's possible that something in that area could be the cause.
One possible plot could be that Harry is under a powerful dark spell. The transformation into a dragon might be a part of a scheme by Voldemort or his followers to either discredit Harry or use his new form for some evil purpose. Maybe Harry has to learn to control his dragon form in order to fight back and protect Hogwarts and his friends.
Well, if Harry Potter turns into a gorgon in fanfiction, he would probably have some really cool and terrifying powers. He could turn people to stone just by looking at them. Maybe he'd struggle to control this new ability at first and accidentally petrify some of his friends. But then he'd learn to use it for good, like scaring off Death Eaters or protecting Hogwarts in a very unique way.