Perhaps in the fanfic, Harry is given the chance to relive his first year at Hogwarts. But this time, he has all his memories and skills from his later years. He tries to change things for the better, like preventing Quirrell from getting possessed by Voldemort in the first place. He could also use his advanced knowledge of magic to befriend Hagrid even more and learn more about the magical creatures early on.
A cool plot could be that Harry enters a magical tournament not related to the Triwizard Tournament. In this tournament, he has to face challenges that are designed to test his loyalty, courage, and wisdom in ways that the original Triwizard tasks didn't. For example, he might have to make a choice between saving a group of students or retrieving a powerful magical artifact that could help in the fight against the dark side. And all the while, he has to deal with some students who are jealous of his fame and try to sabotage him.
You can start by mixing different magical abilities. For example, create a character who can control both fire and water magic, which is usually not seen in the regular Harry Potter world. This would make them stand out.
A really interesting plot could be that the reborn character is actually a huge Harry Potter fan in their previous life, so they know all the secrets and prophecies. They use this knowledge to their advantage. For instance, they might be able to figure out how to defeat Voldemort more quickly by using a combination of things they remember from the books and their own new ideas. They could also change the relationships between characters. Instead of Harry and Hermione just being friends, the reborn character could nudge them towards a romantic relationship earlier on, which would then have a ripple effect on the whole story.
Well, you could have a fanfic where Voldemort uses DND - style dark magic to open portals to other dimensions. The Order of the Phoenix has to quickly learn DND - style combat and magic rules to fight off the new threats that come through these portals. Harry could be sent on a special mission to find a DND - style mage who can teach them the counter - spells. Meanwhile, the Death Eaters are also trying to master this new form of magic for their own evil purposes. This would create a really exciting and unique story.
Perhaps a plot where the protagonist can choose to either side with the Ministry of Magic during a time of political unrest within the wizarding world or join a rebel group. This would involve different magical battles and moral dilemmas depending on the choice. In the 'harry potter cyoa fanfic', this could show different aspects of the wizarding society that we don't often see in the original books.
A cool plot for a Harry Potter Twilight fanfic could be a competition. The wizards from Harry Potter and the vampires and werewolves from Twilight compete in a series of challenges. These challenges could test both magic and the unique abilities of the Twilight characters. Or perhaps a love triangle between a Harry Potter character, a Twilight vampire, and a Twilight werewolf. It would be interesting to see how the different cultures and powers interact in matters of the heart.
Another plot could focus on the lives of the secondary characters from the original series. For example, Neville could be the head of Herbology at Hogwarts and discovers a new, dangerous plant that has some sort of connection to an ancient magic. The 'carry on fanfic' could then be about how he and his students deal with it, with some cameos from the main characters.
One idea could be that a dragon escapes from Gringotts and Harry has to use his skills to track it down. Maybe the dragon has a special connection to a powerful dark magic item that Voldemort was after.
One idea could be that Voldemort somehow enters the Runescape world to seek more power. Harry and his friends follow him there to stop him. They have to learn the rules of Runescape quickly to be able to fight Voldemort. Another idea is that a Runescape wizard discovers a portal to the Harry Potter world and brings some of the unique items from Runescape, like special runes, which causes a stir in the wizarding world.
A great plot for a Harry Potter academy fanfic might be a time - travel scenario. A group of students accidentally travel back in time to the founding days of Hogwarts. They have to navigate the different rules and attitudes of that era while also trying not to change history too much. Or perhaps there's a plot where a student is wrongly accused of a major crime at the academy and has to prove their innocence. They'll need to use their wits and the help of their friends to find the real culprit.
Perhaps in the fanfic, the snake is a key to unlocking an ancient magic that has been lost in the wizarding world. This could lead to a whole new adventure for Harry and his friends as they try to understand and use this magic.