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.
One possibility is that Harry Potter becomes a hybrid of a wizard and a centaur. He would inherit the centaur's knowledge of the stars and nature. His lower body being that of a centaur would make it difficult for him to move around Hogwarts in the normal way. He would have to find new ways to get to his classes. And he might be shunned by some students who are afraid of his new and strange appearance, but he could also form new alliances with those who are more open - minded and interested in his unique situation.
One possible plot could be that Issei discovers a hidden power within himself that gradually transforms him into a dragon. This new form gives him enhanced strength and abilities, but also attracts the attention of powerful enemies who want to either control him or eliminate him. He has to learn to master his dragon form while also protecting his friends and loved ones.
One possible plot could be that Astrid is cursed by an evil sorcerer. At first, she has no idea what's happening to her but slowly starts to notice physical changes like her skin getting scaly. As she turns more and more into a dragon, she has to struggle to maintain her relationships with her friends who are initially afraid of her new form. Eventually, she discovers a way to break the curse through an ancient magic ritual.
One possible plot could be that Eragon, while facing a powerful dark enemy, discovers a hidden ancient magic that causes him to transform into a dragon. As a dragon, he has to quickly adapt to his new form, learning to fly and use his newfound dragon abilities like enhanced strength and fire - breathing. He then uses these powers to defeat the enemy and protect his land.
Well, perhaps in this fanfiction, Harry Potter discovers he has some sort of divine connection to the dragon god. Maybe he gains the ability to communicate with dragons and uses their powers to fight against Voldemort. He could also be on a quest to understand the nature of this newfound connection and how it relates to the wizarding world.
In such a fanfiction, perhaps Harry discovers a dragon in the Forbidden Forest. He realizes the dragon is being hunted by dark wizards. Harry, using his skills and magic, decides to protect the dragon. They form a bond as Harry spends time understanding the dragon's needs and communicating with it through magic. Eventually, the dragon becomes his ally in fighting against the dark forces in Hogwarts.
One possible plot could be that Harry has to keep his true dragon form a secret while at Hogwarts. He might face challenges like controlling his dragon instincts during classes or Quidditch games. For example, his natural inclination to hoard things could get him into trouble in the common room when he tries to stash away everyone's shiny objects.
Well, perhaps the plot could involve Harry finding a dragon egg and raising the dragon as his familiar. This would bring a whole new set of adventures as he has to hide the dragon from the Hogwarts faculty who might not be too keen on a dragon on campus. He could also use the dragon's special abilities to his advantage in his battles against Voldemort.
Well, perhaps Harry could discover he has some dragon - like abilities. Maybe he can breathe a bit of fire when he's extremely angry. It would make him even more of an outcast at first, but then these abilities could help him in battles against Voldemort.
Well, perhaps the dragon, being a powerful and wise creature, sees Harry Potter's potential and decides to raise him in a hidden lair. It could teach Harry unique magical skills that are different from what he'd learn at Hogwarts, like how to communicate with magical beasts on a deeper level.