The plot could start with Harry having strange dreams about an underwater city. He becomes obsessed with finding out what these dreams mean. After some research, he discovers a connection to Atlantis. Using a time - turner (even though it's dangerous), he goes back in time to when Atlantis was still above water. There, he witnesses the height of Atlantean magic and civilization. But he also discovers a dark secret that was the cause of Atlantis's downfall. Now, he has to figure out a way to prevent the same thing from happening to the wizarding world while also dealing with the Atlantean magic and the power struggles within the Atlantean society.
Maybe Harry is sent on a mission by Dumbledore. Dumbledore has received some strange prophecies that seem to be related to Atlantis. Harry, along with his friends Hermione and Ron, travel to Atlantis. Once there, they find that the magic in Atlantis is different but related to their own. They have to figure out how to work with the Atlantean magic to stop an ancient evil that has been awakened and is endangering both Atlantis and the wizarding world. It could involve a lot of exploration of the Atlantean culture and magic system, which would be really fascinating.
In such a fanfiction, Harry might use his magic to explore the lost city. He could discover new magical creatures or spells that were lost with Atlantis. Maybe he'd face some challenges from ancient magic defenses there.
Maybe Harry discovers he has some hidden connection to Atlantis. He could be magically transported there and due to his powerful magic and heroic nature, he ends up becoming the king. He then has to deal with Atlantis's internal politics and protect it from external threats.
One possibility is that Harry discovers a hidden magical connection between Hogwarts and Atlantis. Maybe he is magically transported there and through his unique powers from Hogwarts, he begins to assert his influence. For example, he could use his knowledge of spells to solve problems in Atlantis that the local wizards or mages couldn't. Another aspect could be that he uncovers a dark secret in Atlantis related to the Dark Arts, and he has to use his Gryffindor courage to face it and in the process, becomes a respected figure and eventually the ruler.
One possible plot is that Voldemort also has an interest in Atlantis. Harry, as the King of Atlantis, has to not only protect his new kingdom but also prevent Voldemort from getting his hands on Atlantean power sources. This could lead to epic battles underwater, with Harry using his Patronus and other spells against Voldemort's dark magic, all while trying to uphold the traditions and values of Atlantis.
Yes, there are likely some fanfics out there that blend the two. Some fans might be intrigued by the idea of Harry Potter characters exploring the lost city of Atlantis, with its own unique magic and secrets. It could involve Harry and his friends on a quest in Atlantis, facing new challenges and perhaps even learning new types of magic.
One idea could be that the Ministry of Magic discovers a connection between Atlantis and a powerful dark magic. Harry and his friends are sent on a mission to Atlantis to stop a dark wizard from awakening an ancient evil there. They'd have to navigate the unfamiliar Atlantean magic and the strange underwater environment.
In some fanfics, Harry could find out he has distant relatives from the Potter family who live in a far - off land. These relatives could be part of a different wizarding culture. When Harry meets them, he gets to learn about different types of magic and different ways of living in the wizarding world. He might also discover that his family has a much bigger role to play in the overall wizarding history than he thought.
One possible plot could be that Harry stumbles upon the Sword of Gryffindor in a hidden chamber in the Forbidden Forest. Maybe he's on a solo quest to find a powerful weapon against Voldemort and the magic of the forest guides him to it. Then he has to figure out how to use its power to his advantage in the upcoming battles.
The snake could be an injured or lost magical creature. Harry, being the kind - hearted person he is, decides to take care of it. As he does, he realizes that the snake has a connection to a powerful wizard or witch who has been lost for ages. This connection then draws Harry into an adventure to find out what really happened to that powerful figure and how it affects the present state of the wizarding world.
Well, perhaps in this fanfiction, Harry Potter stumbles upon a lost baby in the wizarding world. He might then take it upon himself to find the baby's parents. Maybe he uses his magical skills, like casting spells to track the family. He could also seek help from his friends at Hogwarts, like Hermione who would surely be resourceful in finding clues about the baby's identity.