Who could be the 'Lost King' in a 'Harry Potter' fanfiction?

The 'Harry Potter Lost King' fanfiction might center around a prophecy. There was a king long ago who was lost in a battle or some dark magic. Harry Potter, with his penchant for getting involved in things related to the greater good, discovers that he has a role to play in finding this king. It could involve exploring ancient wizarding libraries, deciphering old spells, and enlisting the help of his friends at Hogwarts to figure out where the lost king is and what his return means for the future of the wizarding realm.

Perhaps it could be a king from a fictional, magical kingdom that has some connection to the wizarding world. For example, a king from a neighboring magical land who has always been curious about Hogwarts and the magic that Harry wields. He and Harry could meet during some diplomatic mission between their two realms.

It could be an entirely new character created just for the fanfiction. Maybe a long - lost wizard who was turned into a vampire and then gained enough power to become a king among them.

It could be a former Hogwarts student who was expelled for some misunderstood reason. This person, full of bitterness, decides to make a name for himself in the seedy underbelly of the wizarding world and becomes the 'street king'.

It could be Captain Hook. Since Harry Potter has magic, Hook might see him as a huge threat to his plans in Neverland. He would try to capture Harry and use his magic for his own evil purposes, or simply get rid of him to maintain his control over the island.

It could be a dark wizard who has some connection to the sea. Maybe he wants to stop Harry from reaching a certain destination in the sea.

King Arthur. He is a symbol of chivalry and justice. He could instill in Harry the values of honor and courage. Arthur's knowledge of magic, which might be different from the modern wizarding world's magic, could give Harry a unique advantage. He could also introduce Harry to the concept of a round table of wizards, where everyone is equal and has a voice in the fight against evil like Voldemort.

A less obvious candidate could be a corrupted Dumbledore. Imagine if he was swayed by the allure of absolute power and became the dark king. It would be a huge twist as he is seen as a symbol of good in the original books.

Perhaps some of the magical creatures that Harry has befriended over the years, like the centaurs or the house - elves, could become his allies. They could offer their unique skills and knowledge to help Harry in his new role, and Harry, in turn, could work towards better rights and treatment for them in the wizarding world.

Perhaps a magical creature that has made the island its territory. This creature doesn't want outsiders like Harry and his friends interfering. It sees Harry's glasses as a strange and foreign object and will do anything to keep them from leaving the island. It could be a giant spider - like creature that spins webs to trap intruders, just like the acromantulas in the Harry Potter series.