The plot might develop from a prophecy. A prophecy in the Harry Potter world predicts a great danger that can only be averted by the combined forces of both worlds. Characters from both universes are then drawn together. They initially struggle to trust each other due to their different ways of life and values. However, as they face the first signs of the impending doom, they realize that they have to put aside their differences. They start to train together, sharing their knowledge and skills. As they get closer to the source of the danger, they discover that an old enemy has found a way to merge the two worlds in a chaotic and destructive way, and they must race against time to stop it.
The plot could start with a mysterious portal opening between the two worlds. A Hogwarts student might accidentally stumble through it into the world of Strike the Blood. This would lead to a series of adventures as they try to find their way back home. Along the way, they could meet the characters from Strike the Blood and learn about their world. The student could also introduce some basic magic concepts to them. As news of this strange visitor spreads, it could attract the attention of both the good and bad forces in the Strike the Blood world, creating a lot of tension and action.
A possible plot development could be centered around a powerful magical artifact. In the Harry Potter world, an ancient and powerful relic has been stolen and somehow ends up in the world of Strike the Blood. A group of Hogwarts students, along with some of the Strike the Blood characters, must work together to retrieve it. They face many challenges as they have to deal with different cultures, magic systems, and power - hungry villains who also want the artifact for themselves. As they progress, they start to understand and respect each other's worlds more, leading to new friendships and alliances.
The plot could start with a dark spell or some kind of mind - altering event that turns Harry into the Joker - like figure. Then, he might start attacking the very people he once protected, like his classmates at Hogwarts. This would create a lot of chaos within the school walls. The teachers would be at a loss on how to deal with him, as his magic combined with the Joker's unpredictable nature would be a very difficult combination to handle.
The plot could start with Harry escaping the Dursleys earlier than in the original. He then roams around, trying to find a place to belong. He might stumble upon some hidden magical secrets in the Muggle world that are related to his parents. As he grows, he starts to attract the attention of both good and bad wizards. Some might want to help him, while others see him as a threat because he's an unknown factor, not following the normal wizard upbringing.
The plot could start with Harry's birth into the Weasley family. He'd grow up with the Weasley values and traditions. As he gets older, he might discover his true identity in a different way. Maybe he'd find out he has some special connection to Voldemort that's not related to his parents' death. His relationships with the other Weasley siblings would be key. For example, his bond with Percy could be different, as they'd be brothers from the start. And he'd have a different role in the fight against Voldemort, perhaps leading the Weasley family in the battle more directly.
A really interesting plot development could be the connection between Loki's magic and the magic of the wizarding world. Harry could start to experiment with combining the two types of magic. For example, she might use Loki's magic of deception to create false horcruxes to mislead Voldemort. This could lead to a complex web of intrigue as Voldemort tries to figure out which are the real horcruxes and which are the fakes. At the same time, Harry could be exploring her relationship with her father through memories or encounters with Loki's essence, which would add a whole new emotional and character - driven aspect to the story.
The plot could start with Harry being found by a samurai clan. He'd grow up learning their ways. Then, when he discovers his magical heritage, he has to blend the two worlds. Maybe he uses samurai skills to fight dark wizards.
In this fanfiction, the plot might revolve around Harry's struggle to balance Kreacher's teachings with the values of the wider wizarding world. He could face discrimination from other wizards who are suspicious of his upbringing. Meanwhile, Voldemort might see Harry as an even greater threat because he's been raised by Kreacher. Kreacher, being protective, tries to shield Harry from the Dark Lord, but Harry realizes he has to take a stand. This could lead to a series of battles and adventures where Harry has to prove himself not just as a wizard, but as a person with his own set of beliefs.
One interesting crossover could be in a world where the magic systems of both Harry Potter and Strike the Blood interact. For example, the wizards from Harry Potter might be intrigued by the vampire powers in Strike the Blood. They could study the unique way vampires in Strike the Blood gain and use their abilities, while the vampires might be fascinated by the complex spells and potions of the Harry Potter universe. Another aspect could be the characters' reactions. Harry Potter himself might be cautious yet curious about the vampires, and the protagonist of Strike the Blood could be in awe of the Hogwarts castle and the magic taught there.
The plot could develop in a very dark way. Harry might start hunting down the Order of the Phoenix members. He would be using his knowledge of the good side to help the Death Eaters. For example, he could lead them to the secret passages in Hogwarts.
If Harry Potter snapped his wand in fanfiction, the plot could take a really interesting turn. Harry would be at a significant disadvantage. Enemies might see this as an opportunity to attack him. However, this could also be the start of a new adventure. He could go on a quest to find a magical artifact that could replace the function of his wand. Along the way, he would face numerous challenges and learn more about the deeper secrets of the wizarding world. This could also affect his relationships. Some might distance themselves from him, while others would stand by him more firmly, adding more drama to the story.
One idea could be that the blood test is a school project at Hogwarts. Students are required to do a detailed analysis of their own blood magic. Hermione would be super - excited and dig deep into research. Harry might be a bit worried as his blood has some unique connections to Voldemort. Ron, on the other hand, could discover something unexpected about his Weasley bloodline that has been lost in history.