A great plot for a Harry Potter x Loki fanfiction could be that there is a rift in time and space which brings Loki to the time of Harry Potter. At first, he tries to use the situation to his advantage, but he soon realizes that there are forces at work in this new world that are far more dangerous than he thought. Harry and his friends are initially suspicious of Loki, but as they see his power and his willingness to help (albeit in his own way), they form an alliance. Loki could introduce some Asgardian magic concepts to the wizards, and in return, he learns about the unique magics of the wizarding world. They could then work together to stop a dark force that is trying to take over both the wizarding world and Asgard by using the power of the rift.
Well, a plot could be Loki disguising himself as a Hogwarts student. He gets involved in the house rivalries and eventually meets Harry. They start off as adversaries but then realize they both have a common goal of protecting the wizarding world from a hidden danger. For example, an ancient evil that is about to be awakened. Loki could use his Asgardian knowledge and Harry his wizard skills to defeat it. Also, Loki could be interested in the magic of the wizarding world and want to learn more, leading to some humorous and interesting interactions with the Hogwarts professors.
In 'Loki adopts Harry Potter' fanfiction, it could be that Loki adopts Harry due to some sort of prophecy. Loki realizes that Harry is crucial in a much larger plan involving both the wizarding world and the Nine Realms. So, he takes Harry under his wing. He might train Harry not only in magic but also in strategy and deception. Harry could then use these skills to form alliances within the wizarding world that were previously unthinkable, like getting the Slytherins to side with him against Voldemort by using Loki - inspired tactics.
One idea could be that Fem Loki, being a mischief - maker, gets transported to the Harry Potter world and decides to play pranks on the Hogwarts students. She might turn the Quidditch pitch into a giant ice rink just for fun.
A third plot idea is that fem Harry Potter is actually a long - lost relative of Loki in some convoluted way. This discovery leads to a series of events where they have to work together to uncover the truth about their shared heritage. Along the way, they face opposition from both the wizarding community who fear her newfound connection and some Asgardians who don't trust an outsider.
Well, in such fanfictions, one idea could be the exploration of how the magical world of Harry Potter and the mythological realm of Loki interact when such an unexpected situation occurs. Maybe it shows how the characters from both universes deal with the concept of male pregnancy, which is quite different from the original storylines in both.
Perhaps Loki and Harry find themselves in a situation where they have to swap powers for a day. Loki has to deal with Harry's magic wand and spells, while Harry has to handle Loki's shape - shifting and illusions. This could lead to a series of comical and also character - building moments as they learn from each other.
Maybe Alucard is a time - traveler who accidentally ends up in the era of Harry Potter. He initially has his own agenda but gets involved in the fight against Voldemort. His unique powers, which are very different from the magic in the wizarding world, make him both an asset and a mystery. Harry and his friends are both fascinated and a bit afraid of him. Alucard could also introduce a new type of magic or power that the wizards have never seen before, which could change the balance of power in the war against the Dark Lord.
One idea could be that a character from Harry Potter, like Hermione, accidentally gets transported to Storybrooke. She could use her magic knowledge to help the residents solve a mystery that has been plaguing the town. Maybe it's a spell that has gone wrong and is causing strange things to happen, and her logical thinking and spell - casting skills would be very useful.
One idea could be that Slenderman somehow enters the wizarding world of Harry Potter. Maybe he's drawn by the powerful magic there. He could start causing strange disappearances in the Forbidden Forest, and Harry and his friends have to figure out how to stop this new, otherworldly threat using both their magic skills and their knowledge of the wizarding world's secrets.
One plot idea could be that a Kitsune disguises itself as a student at Hogwarts to learn more about human magic. It could get involved in Harry's adventures and use its Kitsune abilities, like shape - shifting or illusion - casting, to help or sometimes cause trouble. Another idea is that a Kitsune is a guardian spirit of an ancient magical place near Hogwarts, and Harry discovers it during one of his explorations. The Kitsune then becomes an ally or a guide for Harry in uncovering secrets about the wizarding world.
One idea could be that Shikamaru, with his strategic mind, gets transported to the wizarding world of Harry Potter. He could use his intelligence to help Harry and his friends in their battles against Voldemort. For example, he might come up with unique battle plans that the wizards hadn't considered before, like using the environment in Hogwarts in unexpected ways during duels.