What are some interesting ideas for a High School DxD fanfiction?

A third concept could be a killer who was once a victim of the dark side of the High School DxD universe. They now seek revenge on those who wronged them. However, as the story progresses, they realize that revenge is not the answer and end up joining forces with the good guys to make the world a better place.

One idea could be to explore a new character reincarnating into the High School DxD world with a unique power, like the ability to control time in small bursts. This could lead to some really interesting plot twists, such as being able to freeze time during battles or rewind to correct mistakes. Another idea is to have a reincarnated character who has memories of a different type of mythology and tries to incorporate that knowledge into the existing world of High School DxD. For example, if they remember Norse mythology, they could introduce new spells or artifacts related to it. A third idea is to focus on a reincarnated character who is trying to change the fates of some of the main characters. Maybe they know how things are supposed to play out from their past life knowledge and want to make things better for their favorite characters.

One idea could be Livia forming an unexpected alliance with a character like Issei. Maybe she has some unique knowledge about the supernatural world that she shares with him to help in a difficult situation.

You could do a crossover with 'Sword Art Online'. The virtual reality aspect of SAO could be combined with the supernatural elements of High School DxD. For example, the characters could be trapped in a virtual world that has elements of both worlds, and they have to fight their way out. Issei might have to use his skills in a new digital environment while also dealing with SAO - like challenges.

There could be a fanfiction where Sasuke's Sharingan has an unexpected interaction with the supernatural elements in High School DxD. For example, his ability to see through illusions could be enhanced or altered by the magic in that world. This could lead to him having a different role in the battles and relationships within the High School DxD setting.

One idea could be exploring the backstory of an exorcist character in more depth. Maybe they have a hidden past related to the devils in High School DxD that no one else knows about.

Another plot could involve a time - travel scenario. Maybe a character accidentally sends themselves and some of their friends back in time to when the first devils were created. They would have to navigate this ancient world while also trying not to change history too much, or else it could have dire consequences for their present.

One idea could be a comical situation where a character accidentally releases a fart during a tense battle in the High School DxD world, and it somehow disrupts the enemy's attack. For example, the smell could be so bad that it makes the opponents gag and lose their concentration.

One idea could be Leviathan using her unique powers in a new way to solve a mystery within the school. For example, she might use her water - based abilities to uncover hidden passages or secrets. Another could be a story where she forms an unexpected alliance with a character from a different faction to face a common threat.

A possible plot is that the OC is a misfit who doesn't fit into the typical categories in the High School DxD world. They might be a human with no obvious supernatural powers at first, but through their wits and determination, they manage to form alliances with different factions. They could use their knowledge of human technology and psychology to gain an edge, and along the way, they develop a unique power or ability that no one expected.