Use the unique settings of both series. The high school setting in Highschool DxD and the more myth - based settings in Campione can be blended. For example, the high school could be the base of operations for the combined group, but they have to travel to different mythological realms from Campione to gather artifacts or allies. This creates a lot of opportunities for adventure and discovery within the plot.
Develop the characters' relationships carefully. Let's say a Campione character is initially distrustful of the devils in Highschool DxD due to their reputation. But as they face challenges together, they begin to understand and respect each other. This kind of relationship arc can make the story really engaging. You can also introduce sub - plots that explore the different cultures and power systems of the two series. For instance, the Campione's divine powers and how they compare to the magic in Highschool DxD. By doing this, you add depth and complexity to the overall plot. And don't forget to have a satisfying climax where all the characters' growth and the different plot threads come together in a big showdown against the main antagonist.
Maybe in the fanfiction, the Campione characters are invited to the Highschool DxD world to participate in a special tournament. They bring their own unique skills and knowledge, and during the tournament, they form unexpected alliances with the devils, angels, and fallen angels. This would allow for a lot of character interactions and development.
Start with a mystery that ties both universes together. For instance, a powerful artifact has gone missing from Akame ga Kill's world and has ended up in Highschool DxD's world. Characters from both sides must work together to find it. This creates an immediate goal and a reason for them to interact.
First, give the character a unique backstory. For example, if they're a demigod, their godly parent could be a minor deity that was forgotten, which gives them a sense of mystery. Also, give them a distinct personality trait, like being overly curious or having a strong sense of justice. This will make them stand out.
One possible scenario in such a fanfiction could be Shirou Emiya's unique abilities from the Fate series being introduced into the Highschool DxD universe. His projection magic might cause quite a stir among the devils, angels, and fallen angels in that world.
One possibility could be that Ichigo's powers would make him a very unique and powerful character in the Highschool DxD universe. His zanpakuto abilities and high - level combat skills could give him an edge in the battles against the devils and other supernatural beings in that world.
To create a compelling Highschool DxD OC Demon, start with their personality. Are they cunning and sly like a typical demon, or are they more noble - minded? This will shape how they interact with other characters. Next, consider their goals. Do they want to gain power in the demon world, or are they more interested in protecting humans? Also, their relationships with existing characters matter. If they have a rivalry with a well - known character from the series, it can add depth to the story. For instance, if they constantly try to outdo Rias in terms of leadership among demons.
To create a compelling OC in Highschool DxD fanfiction, first think about their backstory. A tragic or mysterious past can add depth. For example, if your OC is an exiled devil, it gives a reason for their actions. Also, consider their powers. Make them unique but not overpowered to the point of being unbelievable. Maybe they have a special ability related to an element like shadow manipulation that ties into the DxD universe's lore.
One idea could be a new character who is a transfer student with a unique Sacred Gear that no one has seen before. This character could disrupt the power balance in the school and create new alliances and rivalries.
You can combine the traits of characters from both series. For example, a character could have the Sharingan from Naruto and the wings of a devil from Highschool DxD. This would give them a very distinct look and set of abilities.
The plot could also involve Naruto being mistaken for a new type of devil or a strange being in the Highschool DxD world. His chakra could be seen as a very unique power source. He might have to go to the high school in the DxD world and get into all kinds of adventures, like dealing with the pervy situations that Issei often finds himself in, but with his own Naruto - style humor and strength.