Maybe a dragon OC that is from a different dimension. In this 'Highschool DxD' fanfiction, the dragon could bring unique magic or technology from its home dimension. It could have a goal to study the human world and the devils' society in the 'Highschool DxD' universe, which would lead to various interactions and adventures.
An idea for a dragon OC could be one that was once a human but was cursed or blessed (depending on how you see it) to become a dragon. This dragon OC could struggle with its new identity, trying to hold on to its human memories and values while adapting to the dragon body. It could join the main characters in their battles and school life, bringing a different perspective to the story.
One idea could be a dragon OC that has the ability to transform into different elemental forms. For example, it can be a fire - breathing dragon in combat situations, but a water - based dragon for healing or stealth purposes. This would add an interesting dynamic to the story as it could befriend different characters based on its form.
A plot could revolve around an OC Dragon God who forms an unlikely alliance with Issei. They could team up to face a greater threat that neither the devils nor the angels are fully aware of. The OC could bring in their unique dragon god powers and knowledge to help Issei level up in a different way, adding a new dynamic to the story.
Well, an interesting plot might involve an OC Dragon God who has lost their memories and has to rediscover their powers and identity while interacting with the characters in Highschool DxD. They could start off as a seemingly ordinary student, but as the story progresses, strange things start to happen that hint at their true nature. Also, an OC Dragon God could come from a different dimension and bring with them unique powers and knowledge that change the dynamics of the Highschool DxD world. Maybe they have a special connection to one of the main characters that has been fated since long ago.
You could write about an OC who is a half - angel, half - devil. Their internal struggle between the two natures and how they fit into the world of Highschool Dxd, trying to find their place among the devils, angels and fallen angels. It could explore themes of identity and acceptance.
An interesting OC for a Highschool DxD fanfiction could be a half - angel, half - devil. Their internal struggle between the two natures would make for a great character arc. They could be trying to find their place in the world where angels and devils have their own agendas, and they don't fully belong to either side.
You could also have a Kitsune OC who is a master of disguise. She uses her Kitsune abilities to transform into different students or teachers at the school to gather information. Maybe she's on a secret mission to find out about the hidden powers within the school. This would add an element of mystery to the fanfiction.
Well, you could create an OC that has the power of prophecy. This OC in the 'Highschool DxD' fanfiction would know about future events and could either try to prevent disasters or manipulate them to their advantage. Maybe the OC is a godlike figure who comes from a different dimension where the rules of power are much different. They introduce new forms of magic or combat techniques that the characters in Highschool DxD have never seen before.
One idea could be creating an OC who has a unique power related to time manipulation. This OC could use their power to turn back time during battles in the 'Highschool DxD' universe, catching opponents off - guard. Another idea is an OC with a power based on sound. They could use sonic waves for offense and defense, like creating a sonic shield or a powerful sonic blast.
One idea could be creating an OC who is a half - angel, half - devil hybrid. This would bring a unique dynamic as they struggle with the opposing natures within them. They could have special powers that are a combination of angelic and devilish abilities, like the power to heal but also to curse. Another idea is an OC from a different mythological background, such as a Norse or Egyptian origin, who gets involved in the Highschool DxD world. This would introduce new elements and cultures into the story.
Another interesting concept is an SI OC who is a transfer student from a different supernatural realm. They bring with them their own set of customs and powers that are completely new to the characters in Highschool DxD. This could lead to some really fun cultural clashes and power exchanges.
A good plot idea could be that the OC Dragon God has to hide their true identity in the high school. They are there to find a certain magical item that is hidden in the school. As they search, they get involved with the main characters and have to deal with the normal high school drama as well as the supernatural threats that come their way.