One interesting concept is to make Hera a part of Harry's family tree in the fanfiction. Maybe she had a relationship with one of his ancestors long ago. This connection could give Harry access to a new type of magic that is passed down through the family. He could then use this magic to face new challenges and enemies that the normal wizarding magic can't handle.
A unique way could be to have Hera send one of her mythical creatures to help Harry. For instance, a magical pegasus that can fly faster than any broomstick and has special powers like healing. Harry could use it to his advantage in battles or to travel quickly to different places.
Well, you could have a dog that has a special connection to the Marauder's Map. Maybe the dog can see the footprints on the map even when it's not fully activated, and it uses this ability to help the characters find their way or catch someone who is up to no good. It would be a really cool and unique way to bring the dog into the 'Harry Potter' universe.
Perhaps a character from the 'Harry Potter' world visits the Muggle world and becomes fascinated with whiskey. They then bring the concept back to Hogwarts but in a magical way. For example, they create a whiskey - infused spell that gives the caster a boost of confidence and strength. This would not only combine the two elements but also explore the cultural exchange between the wizarding and Muggle worlds and how magic can be influenced by Muggle items like whiskey.
Another way to combine them uniquely is through a time - travel plot. Harry Potter could be sent back in time to a period when Doctor Fate was first learning his powers. Harry's knowledge of magic could help Doctor Fate in some way, and in return, Doctor Fate could teach Harry some secrets of the universe that would help him in his fight against Voldemort in the future. This would create an interesting dynamic between the two characters from different universes.
You could also create a scenario where a curse has been placed on both of them that links their fates. In order to break the curse, they need to understand each other completely. So, they start spending a lot of time together, sharing their stories, fears, and hopes. This deep connection could then evolve into a yaoi relationship. Harry's experience with the wizarding community and El Tigre's experience with his family and the city he protects all play a role in how they interact and fall for each other.
One creative way is to have a soldier from a parallel magical world come to the 'Harry Potter' universe. This soldier could bring new spells or combat techniques that Harry and his friends have never seen before. It would add an element of mystery and newness to the story.
One creative way is to have a time - travel plot. A character travels back in time to learn about a long - lost surgical technique from the founders of Hogwarts era. For example, Salazar Slytherin might have known a dark - magic - influenced surgery that could be adapted for good. Another way is to introduce a new magical disease that requires a blend of Muggle and wizarding surgical knowledge. So, a character like Luna could bridge the two worlds in finding a cure.
Naruto could have a snake summoning contract instead of toads. This would completely change his combat style and the types of allies he has. He could summon different kinds of snakes with various abilities like poison, constriction, or even the ability to fly.
A really unique combination would be if the Digital World was a parallel dimension to the Fairy Tail world, and there were rifts between the two. The Digimon and Fairy Tail characters could accidentally fall through these rifts into the other world. In the Digital World, the Fairy Tail wizards would have to adapt to the digital environment and learn how to work with Digimon. Meanwhile, in the Fairy Tail world, the Digimon would have to deal with the chaos of the magic - filled world. This could lead to some really interesting character development and plot twists. For example, Gray might freeze part of the Digital World by accident, or a Digimon might accidentally eat some of Erza's cake and she'd be furious. There could be a lot of comical and action - packed moments as they figure out how to get back to their respective worlds.
Maybe their powers could combine through a magical artifact. Say they find an ancient talisman that links their powers. When they touch it together, their powers merge, allowing Ichigo to use his Bankai with a Quincy - like energy enhancement, and Candice to have access to some of Ichigo's Hollow - based speed and agility. This could open up a whole new range of combat abilities for both of them.
Foxes could be part of a new magical species in the fanfiction. They could have their own language and culture within the wizarding world. For instance, they might live in a hidden part of the Forbidden Forest and have a special connection to nature magic that the main characters need to understand to defeat a new dark force. This would expand the world - building in the fanfiction.