How could a Crossover Fanfiction of Rin, Shirou, Saber and Astaroth in DxD Incorporate Their Abilities?

Well, a fanfiction like this could be really interesting. Maybe it could start with Rin and Shirou being somehow transported to the DxD universe. Saber could end up being a powerful ally or a mysterious figure that both the devils and the heroes in the DxD world are curious about. And Astaroth, being a powerful demon in the DxD lore, would surely have an interesting dynamic with the Fate characters. It could be a story full of magic battles, political intrigue within the devil society, and the clash of different ideologies from Fate and DxD.

One way the fanfiction expands on the characters is through their interaction with new elements. Shirou, who was mainly dealing with his own world's magic system, now has to deal with Saber's different magical heritage. This forces him to adapt and learn, showing his intellectual side more. Saber, being from a different time and place, in a crossover might have to face modern - day ethics and values. This challenges her traditional beliefs and shows how she can either hold on to them or evolve. Their relationship in the crossover also allows for exploring their mutual respect and how they can support each other in ways that were not as evident in the original story.

A plot could revolve around a spell gone wrong that merges the two worlds partially. Saber finds herself in a strange new world filled with devils, angels, and fallen angels. She might initially be confused but quickly adapt. Her presence could disrupt the balance of power in Highschool DxD. For example, the devils might see her as a threat or an opportunity to gain more power. And Saber would have to navigate this new world while trying to find a way back to her own world.

One possible scenario in such a fanfiction could be Shirou Emiya's unique abilities from the Fate series being introduced into the Highschool DxD universe. His projection magic might cause quite a stir among the devils, angels, and fallen angels in that world.

Saber is often a symbol of honor and power, and in relation to Rin, they can be written in fanfiction as two characters who grow to understand and respect each other more. Rin's knowledge of magic can be a key factor in their interactions. However, when it comes to lemon fanfiction, it's not a proper area to explore their true characters as it usually involves vulgar content.

To create an engaging OC for a Highschool DxD Astaroth fanfiction, think about their goals. Are they seeking power, revenge, or something else? This will drive their actions in the story. Also, consider their relationships. How do they view Astaroth at the start? Do they fear, respect, or love him? Their initial attitude can change over the course of the fanfiction, creating a character arc. And don't forget about their skills. If they have a special power or ability, it should be something that ties into the overall plot and their interactions with Astaroth.

The plot could revolve around their adventures together as a married couple. Maybe they discover a new magical threat and have to use their combined powers and skills, with Shirou's swordsmanship and Rin's magic, to protect their world. They also might start a family and raise a child with magical abilities, passing on their knowledge and values.

One popular 'Saber x Rin x Shirou' fanfic is 'The Three's Bond'. It beautifully weaves their relationships together in an alternate universe setting. The story shows how they support each other through various challenges.

The idea of sacrifice also pops up a lot. Given the nature of the Fate series, the characters may be in situations where they have to sacrifice for one another. In fanfics, this can be explored in different ways, like Saber sacrificing her power to protect Rin and Shirou.

Perhaps they face challenges from the magical world. Since Saber has a connection to the throne of heroes, there could be threats from other entities who don't want a married Saber. They would have to fight together to protect their relationship and their new life. Meanwhile, they are also growing closer and deeper in love as they face these difficulties side by side.