Perhaps an OC that is a descendant of an ancient and powerful magical being. This OC could have access to long - lost spells and magic that no one in the current Highschool DxD universe has seen. Their presence could disrupt the existing power balance and lead to new alliances and rivalries as different factions either try to recruit or eliminate them.
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 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.
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.
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.
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.
Another plot could involve the OC being sent by an unknown force to either help or hinder Lucifer. They initially seem like an enemy but as the story progresses, it's revealed that they are actually on the same side. They could team up to fight against a common threat to the devil world, like an ancient evil that is starting to rise again.
One idea could be an OC demigod who has the power of a forgotten god. They could use this power to help the main characters in unexpected ways, like having the ability to manipulate time on a small scale during battles. Another plot could involve the OC demigod trying to find their place in the world of Highschool DxD, being half - god and half - something else. They might struggle with acceptance from both the devil and angel factions.
One idea could be an OC who is a gamer and discovers a hidden power within the Highschool DxD universe while playing a virtual reality game related to it. This power could be something unique like the ability to control shadows in the DxD world.