One possible scenario in such a fanfiction could be that the magical elements from Harry Potter, like spells and potions, are introduced into the Highschool DxD world. Maybe a character from Harry Potter somehow ends up in the Highschool DxD universe and has to deal with the different rules and threats there. For example, a Hogwarts student might be shocked by the devils and angels in Highschool DxD. Regarding the 'death' aspect, it could be a central plot point where a character's death (either from Harry Potter or Highschool DxD) sets off a chain of events that forces the two worlds to interact more closely.
One idea could be a crossover where a character from Harry Potter, say a young wizard, accidentally gets transported to the world of Highschool DxD. He then finds himself in the middle of the harem situation that is common in Highschool DxD. Maybe he uses his magic in unexpected ways in this new world.
It could be really interesting. Maybe the magic from Harry Potter could be introduced into the world of Highschool DxD. For example, the wizards could use their spells in the battles that happen in Highschool DxD. The characters from both universes might interact in unexpected ways. Harry Potter characters could be shocked by the different types of beings in Highschool DxD, while the characters from Highschool DxD could be fascinated by the magic of Harry Potter.
The magic system in Harry Potter could be integrated by having characters from Highschool DxD learn spells. For example, Issei could learn the Wingardium Leviosa spell to lift objects during battle, giving him an unexpected advantage. The Portkey concept could also be used to transport characters between the two worlds quickly.
Yes, there might be. The 'fanfiction' world is vast and diverse. There are often crossovers that combine different popular franchises in unexpected ways. However, the quality and nature of such a fanfiction can vary greatly. Some might be really creative, while others could be a bit of a mess.
A more complex fanfiction could be about a joint mission between the two universes. The leaders of both worlds realize that there is a common threat that only the combined forces of Highschool DxD and Naruto can defeat. So, they send their best characters, like Rias and Sasuke, to work together. This would involve a lot of character development as they learn about each other's cultures and powers.
A story could also revolve around a quest that involves both Diablo and Highschool DxD elements. The characters from both universes could team up to find a powerful artifact that has significance in both worlds. They would need to overcome their differences and work together, with the devils and angels from Highschool DxD learning about the dark and dangerous forces from Diablo.
One idea could be a crossover where Naruto characters are transported to the world of The Highschool of DxD. For example, Naruto himself could end up at the high school and his ninja skills would be quite a shock to the devils and other beings there. He might get involved in the Rating Games, using his shadow clones and other jutsu to his advantage.
One idea could be a crossover where the protagonist from DarkSiders ends up in the world of Highschool DxD. Maybe he has to navigate the complex social and supernatural hierarchies there while also trying to find a way back to his own world. He could bring his unique combat skills and abilities from DarkSiders and use them in the battles that often break out in the Highschool DxD universe.
One idea could be that Ben Tennyson somehow ends up in the world of Highschool DxD. Maybe his Omnitrix gets a strange power-up that transports him there. He could use his alien forms to interact with the characters in DxD, like using Four Arms in a fight against some of the devils or fallen angels.
A fanfiction could focus on Ichigo attending the school in Highschool DxD. His presence would surely disrupt the normal balance. He might not be interested in the whole 'devil' and 'angel' thing at first, but gradually get involved. He could also introduce some of his Soul Reaper training methods to the students there, which would be very different from what they're used to.