Well, Robin is a popular character in these fanfictions. He can bring a different dynamic to the relationship between the knight, the prince and Batman. His youth and eagerness can contrast with the more serious knight and prince. Also, Catwoman might be there. She has her own complex relationship with Batman, and in these fanfictions, she can interact with the knight and prince in interesting ways, whether as an ally or a foe.
Well, one common theme is the concept of redemption. Maybe the knight or the prince has a dark past, and like Batman who is often haunted by his own demons, they are seeking to make up for their past misdeeds. Additionally, the theme of sacrifice is quite prevalent. They might be put in situations where they have to sacrifice their own desires or safety for the greater good, just like Batman is always willing to put himself in harm's way for Gotham.
Perhaps the 'knight' is a new character created specifically for this fanfiction. This character could be a symbol of hope and justice, just like Batman, but with a more knightly code of conduct. Their marriage could be a way to introduce a new dynamic to the Batman universe.
In many fanfictions, Jason saving Batman in 'Batman Arkham Knight' often shows a new side of their complex relationship. It could be a moment of redemption for Jason. Maybe he realizes the true meaning of Batman's mission and decides to put aside their differences. This scenario allows for deep character exploration.
A popular 'Batman Dark Knight' fanfiction is 'Joker's Last Laugh'. It offers a different take on the Joker's final plan and how Batman counters it. The story is full of twists and turns. Then there's 'Robin's Return in the Dark Knight Era' which imagines Robin making a comeback during the events of 'The Dark Knight'. It gives a fresh perspective on how the dynamic between Batman and Robin could have been in that darker version of Gotham.
A popular 'Batman The Dark Knight' fanfiction is 'Batman and the Secret Society'. In this story, Batman discovers a hidden society within Gotham that has been pulling the strings all along. 'The Dark Knight's Final Battle' is another one that's full of action. It pits Batman against a powerful new villain. And 'Harley Quinn's Redemption Arc' is a great read for those interested in seeing the character develop in a different way than in the official canon.
There's a fanfic called 'Arkham Knight: Riddler's New Game'. This one is really interesting as it puts the Riddler in a situation where he has to team up with Batman, albeit unwillingly, to stop a greater threat in Arkham City. The dynamic between the two is explored in a whole new way, with the Riddler's riddles becoming more of a tool for cooperation rather than just a means of taunting Batman.
One common theme is the idea of love and loyalty. The relationship between the character marrying the knight and Batman or the knight within the Batman world often involves deep emotional bonds. Another theme could be adventure, as they might be involved in Batman - style adventures together.
Writing a good 'Batman Dark Knight' fanfiction starts with research. Watch the movie multiple times to catch all the details. Pay attention to the dialogue style. Then, think about what you want to add to the story. It could be exploring the emotional state of the characters more. For example, how did Harvey Dent really feel about his transformation into Two - Face? Build your plot around that. Also, make sure your grammar and spelling are correct, as it can be distracting if there are too many errors in your fanfiction.
There are fanfictions that explore Poison Ivy's backstory in the Arkham Knight world more deeply. For example, a story might focus on her early days and how she came to have such a strong connection with plants. This can add a lot of depth to her character in the context of the game's lore.