I'm not sure specifically as there could be many different takes in such a fanfiction. It might involve Naruto somehow being in a world related to Mordred and taking on the role of a father figure. Maybe it's a crossover where Naruto's values and abilities influence Mordred's growth in a new and unique story setting.
Often, the clash of their different cultures and abilities is an interesting plot point. For example, Naruto's use of ninjutsu and Mordred's magic. Their different moral compasses also play a role. Naruto is more about friendship and protecting the village, while Mordred has her own set of values from the Arthurian world.
One popular 'naruto and mordred fanfiction' is 'The Unlikely Alliance'. It explores how Naruto, with his ninja skills, teams up with Mordred from the Arthurian legend in a world filled with magic and ninja arts. They face common enemies and learn from each other's strengths.
You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own (AO3). Just type in 'naruto father of mordred' in their search bars and see if any relevant stories come up.
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.
Yes, in some fanfictions, Merlin is written as Mordred's father. Writers often like to explore different family relationships and backstories in fanfiction, and this is one such interesting take on their relationship.
There could be. Fanfiction writers often come up with very creative and unexpected crossovers. In a 'fem Harry Potter is Mordred' fanfiction, the author might give the female Harry Potter some of Mordred's characteristics or a backstory related to the Arthurian lore. It could be an interesting exploration of different mythologies and fictional universes combined.
A possible plot could be that there is a disturbance in the balance of the Naruto world. The sages believe that only a being from another realm can help. Naruto is chosen to perform the summoning. He summons Mordred, and at first, they don't get along because of their different backgrounds. But as they learn more about each other and the true nature of the threat, they form an alliance. Mordred teaches Naruto some new combat techniques, and Naruto shows Mordred the value of friendship and loyalty in his world. Eventually, they defeat the enemy and Mordred may or may not decide to stay in the Naruto world depending on how their relationship has developed.
One unique aspect is the clash of two very different universes. Naruto's world of ninjas with chakra and Mordred's more medieval - like world with its own set of magic and combat styles. This creates a really interesting backdrop for the story.
There could be a fanfiction where Merlin has a premonition about Mordred's true destiny. He decides to take matters into his own hands and tries to change it. But this could have unforeseen consequences, like making Morgana more determined to see Mordred fulfill his 'destined' role.