Archer from the Fate/stay night series is often a popular choice for crossovers. His cool and somewhat aloof personality can create interesting interactions with other servants.
One interesting concept could be the unique interactions between servants from different Fate series. For example, seeing how a heroic spirit from one era would react to another's fighting style or personality.
Medea is also a great option. Her complex personality, including her dark past and her powerful magic, can add depth to the fanfiction. The OC could either be an ally trying to redeem her or someone who has to face her as an enemy.
Archer EMIYA is very commonly written about. His complex character, with his brooding nature and powerful abilities, makes him a favorite among fanfiction writers. He has a lot of room for character development in different scenarios. Another one is Saber. Her iconic status in the Fate series means that she often appears in fanfiction. Writers like to explore different aspects of her personality and her relationships with other characters.
One idea could be to explore how Hercules' incredible strength affects the Fate universe. Maybe he is summoned as a Servant in a Grail War and his brute force challenges the traditional battle strategies of other Servants. His Twelve Labors could also be incorporated in some way, like each Labor being a trial he has to face within the context of the Fate story.
A third idea is a crossover where the characters from both universes have to team up to face a common enemy. Maybe an ancient evil that threatens both the world of Fate and the DxD world. They would need to combine their powers and strategies, like the devils using their demonic powers along with the Servants' unique abilities.
Yes. In Fate Extella, the ability to switch servants in the story is a key feature. It allows for different gameplay experiences as each servant has unique abilities. For example, some servants are better at combat, while others might be more useful for exploration or puzzle - solving within the story. The game is designed to give players the flexibility to choose the servant that best suits their playstyle at different parts of the story.
One great 'Fate Servant Crossover Fanfiction' is 'Fate/Grand Order and the World of Harry Potter'. It combines the magic of the Harry Potter universe with the unique Servants from Fate. The story often has interesting battles where Servants use their powers in the Hogwarts setting. Another one could be the crossovers with the Naruto world. Here, Servants might face off against ninja techniques, creating a whole new dynamic of power clashes.
Another concept is a more comical crossover. Shirou tries to adapt to the different rules and magic in the Fate Apocrypha world. He constantly gets into funny situations as he misunderstands the local customs and magic systems. For example, he tries to cook using Apocrypha - style magic ingredients and chaos ensues.
To switch servants in the story of Fate Extella, you need to pay attention to the game's progression. As you move forward in the story, there will be moments when the option to switch is presented. These moments are usually tied to significant events in the game's plot. For instance, after you've defeated a powerful enemy or when you enter a new chapter. The game designers made it this way to ensure that the servant switching is not only a gameplay mechanic but also fits within the context of the story. So, always be on the lookout for these opportunities during your playthrough.