Another theme could be adventure. They might go on quests together, facing various challenges that test their relationship and individual strengths. For example, they could be on a mission to save a kingdom or defeat a powerful enemy.
You can try fanfiction websites like Archive of Our Own (AO3). There are often a lot of well - written Issei x Mordred fanfictions on it. Just use the search function and type in the relevant tags.
To develop Mordred in a Mordred x Highschool DxD fanfiction, her backstory can be explored further. Maybe she has some unresolved issues from her original story that resurface in the Highschool DxD setting. For instance, her complex relationship with her father figure. As she tries to come to terms with these in the new world, she could change and grow. She might also start to question her own values and beliefs as she experiences the different cultures and power dynamics in Highschool DxD, which would be an interesting way to see her character evolve over the course of the fanfiction.
To write this type of fanfiction, you should focus on the relationship development. The fem OC could be from a different land, which adds an element of mystery. Research the Arthurian legends to add authenticity. For the relationship, start with a small moment of connection, like sharing a meal or a common view. Then, as they face challenges together, their bond deepens. Maybe there's a conflict where the fem OC has to choose between her loyalty to her homeland and her growing feelings for Mordred. This creates drama and keeps the readers engaged. Also, use vivid descriptions to bring the world and their relationship to life.
One common theme is self - discovery. Both Mordred and the OC often go through a journey of understanding themselves better because of their relationship. Another theme is loyalty. They usually show great loyalty to each other in the face of various difficulties.
One great fem OC x Mordred fanfiction is 'A New Destiny'. It has a well - developed fem OC who has an interesting dynamic with Mordred. The story dives into their adventures together in the Arthurian world, with great character interactions and a plot that keeps you hooked.
One common theme is the clash of their personalities. Gilgamesh is proud and haughty, while Mordred is rebellious. Their interactions often involve power struggles and attempts to outwit each other.
You can start by looking on fanfiction.net. It has a large collection of Fate - related fanfictions, including ones about Shirou and Mordred. Just use the search function and type in their names.
There's 'A New Path'. In this fanfiction, Mordred is in a difficult situation and Shirou comes to her aid. Their interactions are filled with tension at first, but as the story progresses, it turns into something more like a partnership. It's really interesting to see how they grow together.
Well, you could have a story where Mordred has a past connection to some of the powerful families in the Highschool DxD universe. Maybe she's on a quest to uncover something about her heritage that's linked to that world. And during her journey, she falls in love with one of the characters in an unexpected way. For example, she starts off as rivals with Rias but then they develop a deeper bond as they face challenges together.