One great fanfic could be 'Illya's Adventure in the Magic World'. It explores Illya's journey in a new magical realm with unique challenges and character development.
The light novel follows Illya, who becomes a magical girl. She gets involved in various adventures, often related to the Holy Grail War in a different context compared to the main Fate series. There are battles against other magical entities, and she also has to deal with her own growth as a magical girl and her relationships with the other characters.
The main character is Illya. She is a young girl who becomes a magical girl. Ruby is also important as she is the Kaleidostick that helps Illya in her magical girl activities. Miyu is another significant character, who has her own secrets and plays an important role in the story.
Maybe a time - travel based crossover. A character from Fate Kaleid Liner accidentally travels back in time and meets the younger versions of other characters in the series. This could lead to changes in the timeline and they would have to work together to fix any potential disasters that their meeting has caused, all while trying to find a way back to their own time.
It's about Illya, who becomes a magical girl. She gets involved in various adventures and battles. There are also elements related to the Fate series' lore.
You can combine the traits of different characters from the Fate Kaleid Liner series. For instance, take the magical abilities of one character and the personality of another. This will result in a new and unique character.
It's a visual novel related to the Fate series. It likely involves magical battles, complex characters, and the exploration of different storylines within the Fate universe.