Perhaps Atlantis was once a part of the wizarding world but was lost and forgotten. A group of Hogwarts students, including Hermione, stumbles upon an old prophecy that links Atlantis to the future of magic. They embark on a journey to Atlantis to uncover its secrets and find a way to save the wizarding world from a new threat. Along the way, they learn about Atlantean spells and make new allies among the Atlantean wizards.
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.
One idea could be that Hogwarts students discover a hidden portal to Atlantis during a Care of Magical Creatures class in the Forbidden Forest. They then have to navigate the ancient Atlantean society, which has its own form of magic. Maybe they need to team up with Atlantean wizards to defeat a common dark force that threatens both their worlds.
One idea could be to have the wizards from Harry Potter's world discover the Stargate Atlantis technology. Maybe they could use magic to help repair or understand some of the advanced technology in Atlantis. For example, Hermione could use her vast knowledge of spells and ancient runes to decipher the Atlantis control panels.
A possible plot could involve Percy being sent to Atlantis on a mission by the gods. In Atlantis, he uncovers a conspiracy among some of the Atlantean nobles who are planning to overthrow the current ruling family and take over the power. Percy then has to decide whether to get involved in the internal politics of Atlantis or just focus on his original mission. Along the way, he also learns about the unique culture and magic of Atlantis, which is different from what he's used to in the surface world.
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.
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.
Another interesting concept is a fanfic where Naruto is sent to Atlantis to learn a new form of chakra control. In Atlantis, he meets unique characters who have different ways of using energy, and he has to adapt and learn from them. This could lead to him developing new jutsu.
One idea could be Percy having to face a new underwater threat that is specifically targeting Atlantis. Maybe a powerful sea monster that was once imprisoned by the Atlanteans has been released and Percy has to figure out a way to stop it without causing too much destruction to the underwater city.
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.