Another interesting plot could involve Tiamat forming an unlikely alliance with some of the main characters in Highschool DxD. For example, she teams up with Issei to fight a common enemy that threatens both the devil and her own kind. This would lead to a lot of character development as they learn to trust each other.
One plot idea could be Tiamat adjusting to the modern world in the Highschool DxD universe. Maybe she has to deal with the different social norms and the unique magic systems there.
One interesting 'Highschool DxD Tiamat' fanfiction could be the ones that explore Tiamat's character in the context of the Highschool DxD universe. For example, some fanfictions might focus on her relationships with other characters like Issei. They could show how she adapts to the school environment and the chaos that often ensues in the Highschool DxD world. Another aspect could be fanfictions that delve into her powers and how they are perceived and used within the story. Maybe she uses her powers to protect the school or to help a particular character achieve their goals.
A more complex plot could be centered around a prophecy that foretells the destruction of the Highschool DxD world. The characters then have to embark on a journey to find the source of this prophecy and try to prevent it. Along the way, they discover secrets about their own powers and the true nature of the different factions, and have to make difficult choices that could either save or doom their world.
A third plot idea might be Sona trying to modernize the traditions of the devil world within the context of the school. She could face opposition from more conservative devils, and the story could explore her struggle to bring about change while still maintaining her position and respect.
One idea could be a new character who is a killer but has a hidden noble purpose. Maybe they are targeting rogue devils that are harming humans secretly. This would add an element of mystery and action to the fanfiction.
Maybe Jesus could have a special mission in the Highschool DxD universe. For example, he might be there to stop a great evil that is brewing and uses his powers in a way that is different from the traditional powers in the series. He could team up with Issei and the others, bringing a new dynamic to their group.
One interesting plot idea could be Murayama discovers a hidden power within herself. Maybe she has a connection to an ancient artifact in the Highschool DxD universe that gives her unique abilities, like the power to control time briefly. This could lead to her having to protect this secret from both the devils and the angels in the story.
A possible plot is that a group of students in High School DxD start a gaming club, but they accidentally discover that the games they play are linked to some ancient and powerful magic. As they delve deeper into these games, they uncover secrets about their world and have to face off against enemies who want to use this magic for evil purposes.
One idea could be a new character who is a futa and has unique powers related to both male and female aspects. They could join the Gremory group and cause some interesting dynamics, like having a different approach to battles and relationships within the group.
One idea could be exploring Kuroka's past more deeply in the High School DxD universe. Maybe she has some hidden relationships or secrets from her time before joining the main story's events.
Another interesting plot could be about a joint mission between the two universes. The characters from both Nasuverse and Highschool DxD need to work together to defeat a common enemy that threatens both of their worlds. This would require them to understand each other's abilities and form strategies that combine their unique powers.