A really unique concept could be that the Deathly Hallows from the Harry Potter world are actually artifacts from Asgard that were lost long ago. Loki gets wind of this and decides to come to the wizarding world to retrieve them. Along the way, he forms an unlikely alliance with Harry Potter, Hermione, and Ron. They have to work together to figure out the true nature of the Deathly Hallows and also deal with the dark forces that are after them. This kind of crossover not only combines two very different fictional worlds but also creates a whole new story full of mystery and adventure.
Well, in some fanfictions, Loki might be interested in the Time - Turner device from the Harry Potter universe. He could try to use it for his own purposes, like going back in time to change certain events in the wizarding world to his advantage. Or perhaps Loki and Harry Potter get into a magical duel where Loki uses his Asgardian magic and Harry uses his wizarding spells. The contrast between their different forms of magic would be really interesting to explore in a fanfiction.
One plot could be that Viper has a spell that can control minds, and she uses it on some of the Hogwarts students. Harry Potter discovers this and tries to find a way to break the spell. Loki, being the mischievous one, initially seems to be helping Viper but then has a change of heart and joins Harry to save the day.
One idea could be that Loki, being the mischievous character he is, finds his way into the wizarding world of Harry Potter. He could start causing chaos in Hogwarts, perhaps by disguising himself as a student or a professor and playing pranks that are far more elaborate than those of the Weasley twins. For example, he might turn the entire Great Hall into an ice rink during breakfast time.
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.
One unique aspect is the clash of two different magical systems. Harry Potter's magic is more about spells and potions, while Loki's magic is more of the Asgardian, illusory and shape - shifting kind. In these fanfictions, seeing how fem Harry Potter's more structured magic reacts to Loki's wilder magic is really interesting.
Some unique ideas could be that baby Harry has a special bond with magical creatures from a very young age. For instance, he might be able to communicate with Hedwig even as a baby, through some kind of magical telepathy. This could set up a whole different dynamic in the story.
One idea could be a character who uses Dirty Harry - like tactics to deal with the Death Eaters. For instance, being extremely direct and fearless in the face of danger, much like Dirty Harry in his movies.
A unique Loki Marvel fanfiction idea could be Loki getting trapped in a time loop. Every day he has to relive the same events but tries to find a way to break the loop and change his fate. Or perhaps a story where Loki has to pretend to be another popular Marvel hero and hilarity ensues as he tries to act like them. Another concept is Loki forming an alliance with the villains of the Marvel universe but with his own hidden motives.
In some 'Harry Potter Harem' fanfictions, a unique idea is to have the 'harem' members be those who have been wronged by the dark side in different ways. They bond with Harry as they all strive for justice and a better wizarding world. For instance, a character whose family was destroyed by Death Eaters joins Harry's group. This creates a deep emotional connection among the group members and a strong motivation for their actions. It also gives a new perspective on the fight against evil in the Harry Potter universe, as they work together not just for Harry's sake but for their own and the world's.
A unique idea could be that a Transformer is enchanted by a wizard to be able to use magic. So it becomes a sort of magical - mechanical hybrid. It could use spells like the wizards and also transform into different forms. For example, it could transform into a broom - like form to fly around Hogwarts.
A Harry Potter and Star Wars crossover would be really interesting. Picture Harry and his friends traveling through space in the Millennium Falcon, learning about the Force and using their magic in combination with Jedi skills to fight against a new dark threat that combines the power - hungry Sith and the dark wizards from the Potterverse.