One common theme is mentorship. Arthur often takes on a mentorship role for Harry, guiding him in the wizarding world. Another is family. Since Harry lacks a proper family, Arthur can represent a father - like figure in these stories.
I really like 'Fem Harry: Arthur's Heir in Hogwarts'. In this fanfic, the author portrays how Fem Harry discovers her Arthurian roots and how it changes her perspective within the Hogwarts environment. She starts to see the school not just as a place to learn magic but also as a place where she can uncover more about her ancient lineage. It's interesting to see how she interacts with her friends and teachers, especially those who are aware of her special heritage.
It would probably explore family ties. For example, how the Weasley family would react to the discovery. There might be a whole new level of acceptance and closeness. Also, it could explore the idea of hidden family magic that only comes to light because of Harry's new connection.
Yes, in some fanfictions, Harry Potter is made out to be a descendant of King Arthur. Writers often create this connection to bring in elements of Arthurian legend into the Harry Potter universe, like the idea of a special destiny or the inheritance of certain magical powers or items related to Arthur.
Yes, there are quite a few. You can start by looking on fanfiction websites like Archive of Our Own. Some might focus on how the character inherits Arthurian traits or artifacts in the Harry Potter universe.
Yes, in some fanfictions, Harry Potter is made the heir of King Arthur. Writers often create this connection for the sake of a unique and exciting plot. They might draw parallels between Harry's heroic nature and Arthur's leadership qualities, and use elements from Arthurian legend to enrich the Harry Potter universe in their own creative ways.
One way could be through a prophecy. Similar to how there are prophecies in the Harry Potter series, there could be an ancient prophecy that ties Harry Potter to King Arthur. It could be that Harry has a role to play in restoring some of the lost magic or values of King Arthur's time, like chivalry and honor within the wizarding world.
Arthur might be shocked and immediately want to protect Harry. He could start by confronting those who are abusing Harry or find a safe place for Harry to stay.
Good fanfiction in this regard often has a deep understanding of Arthur's character. It should capture his love for all things Muggle and his inquisitive nature. For example, a story might show him introducing Harry to some unique Muggle artifacts he's collected over the years.