Well, it could be that Naruto's own chakra nature evolves in an extreme way. His Uzumaki bloodline might have some hidden potential that, when combined with his experiences and growth as a ninja, mutates into the ability to control black holes. For example, his chakra, which is already very powerful, could reach a new level where it can warp space to form black holes.
One major consequence could be a shift in the power balance. Naruto's village would become extremely powerful, and other villages might either seek an alliance with them or plot against them out of fear. Also, the natural order of the universe within the Naruto world could be disrupted. Black holes are extremely powerful and their presence could distort space and time, affecting things like the flow of chakra and the stability of ninja techniques.
He might have enhanced physical abilities. Black Widow is known for her strength, agility, and combat skills. Naruto could inherit these, making him an even more powerful ninja in close - range combat. For example, his punches and kicks could be more forceful.
Black Zetsu's story in Naruto is quite the tale. He was an entity that had been around since ancient times. He had an in - depth knowledge of the ninja world's history and used this to his advantage. He was the driving force behind many of the conflicts in the Naruto series. For example, he caused a rift between Sasuke and Naruto at times. His true nature was only revealed towards the end of the series, which was a shock to many characters. He was a master of manipulation, using the desires and weaknesses of others to achieve his ultimate aim of bringing back Kaguya.
One key event was his deception of Madara. He made Madara think he was his ally while actually setting him up for Kaguya's revival. Another was his influence on Obito. He pushed Obito to do things that served his purpose. Also, his role in the Fourth Great Ninja War was significant as he was behind many of the unexpected turns in the war.
In many Naruto Black Rabbit fanfictions, Naruto is the central figure from the Naruto side. He is the one who often welcomes Black Rabbit into his world, whether knowingly or unknowingly. Black Rabbit, on the other hand, is the new element introduced. She could be the catalyst for change in the Naruto universe. Other characters like Sakura might also play important roles, for example, if there is a medical emergency where her skills are needed while Black Rabbit is around. They could learn new medical techniques from each other.
Well, it could be about a really interesting concept where Naruto is somehow related to the idea of a black dragon emperor. Maybe it's a story that combines the powers and elements from Naruto's world with the majestic and powerful image of a black dragon emperor. It might involve Naruto having new powers or facing new challenges in a world where this black dragon emperor concept exists.
In some cases, Kakashi could be a main character. As Naruto's mentor, he might play a crucial role in guiding Naruto when it comes to dealing with the mystery of the black diamond. He could use his wisdom and experience to help Naruto understand the implications of this strange object.
There are fanfictions where the black kitsune is a mysterious being from a forgotten part of the Naruto world. It could be a story where the kitsune has a hidden agenda. For example, it might initially seem like an enemy but is actually trying to protect a great secret that could change the fate of the ninja world. In this fanfiction, the black kitsune's interactions with Naruto and his friends would be full of twists and turns.
First, you need to do your research on both universes. Know the characters, their powers, and the settings well. For example, know all about Naruto's jutsus and Sebastian's demonic abilities. Then, think of a good plot device to bring the two worlds together. It could be a portal or a powerful spell. After that, start with an interesting introduction that hooks the reader, like Naruto suddenly finding himself in the Black Butler's Victorian - era London.