In X - Men fanfiction, an immortal Naruto could be a bridge between different factions. His immortality means he has seen a lot and can understand different points of view. He could try to get the X - Men and other groups, like the Brotherhood of Mutants, to work together. He could share his own stories of how he united different ninja villages in his world, and use his powers to show that cooperation can be more powerful than conflict. Also, his chakra - based powers could be used in creative ways to help mutants who are having trouble controlling their own powers.
He could be a mentor. Given his immortality and vast combat experience, he could teach the young X - Men trainees a thing or two about fighting and perseverance.
In the fanfiction, Naruto's immortality could make him a key figure in resolving long - standing conflicts. He has the time and the power to study both the wizarding and ninja worlds deeply. So he could use his knowledge to find solutions to problems that have been plaguing the wizarding world for ages, like the fight between pure - bloods and half - bloods or the threat of dark wizards. His presence would bring a new dynamic to the story as he doesn't have the same limitations as the regular Harry Potter characters in terms of lifespan and the type of power he wields.
She could be the tech - support person. Given her background, she'd be great at handling all the high - tech gadgets and equipment the X - Men use. She could also be in charge of communication systems during missions.
Hyourinmaru could be a key to unlocking a hidden power within a character. For instance, a young ninja discovers an old scroll that mentions Hyourinmaru. As they study it, they find that it holds the secret to a new form of chakra control related to ice. This then gives them an edge in combat and in their journey to become a stronger ninja.
As a rival. An OC with powers that can match or even outdo Sabertooth's would create intense battles and power struggles. This would keep the story exciting and full of action, constantly pitting their skills against each other.
He could play the role of a disruptor. Just like his character in his own universe, he would disrupt the existing power dynamics in Naruto. His overpowered abilities would make him a force to be reckoned with, whether he's on the side of good or bad.
One possible plot could be that Naruto, being immortal, has seen many things in his long life. He comes to the X - Men universe with a different perspective. He might initially be seen as a threat because of his unknown powers. As the story progresses, he could prove himself useful by helping the X - Men in a big crisis. His immortality would allow him to take risks that others can't, and this could lead to some very exciting storylines. For example, he could sacrifice himself in a way that he knows he'll come back, to save the X - Men from a powerful enemy. This would earn him their trust and he could then start to explore the mysteries of the mutant world further.
He could be a mentor. Since he's immortal, he has a vast amount of knowledge and experience. He could teach young heroes or anti - heroes about the value of life and how to use their powers responsibly. For example, he could guide Robin on how to be more strategic in combat, sharing his own experiences from fighting Voldemort.
One possible plot could be that Naruto is somehow transported to the X - Men universe. He teams up with Wolverine. Naruto's unique ninja skills, like his shadow clones, could be used in combat against the Brotherhood of Mutants. Wolverine could teach Naruto about the concept of mutants and their struggles, and Naruto could in turn show Wolverine some of his ninja wisdom.
One interesting plot could be that Naruto is somehow transported to the X - Men universe. He teams up with Wolverine. Naruto's ability to create shadow clones could be used in interesting ways during battles, like confusing the enemies. Wolverine could teach Naruto some combat skills from the X - Men's fighting style. They could go on a mission to stop a powerful mutant villain who has plans to take over the world, using Naruto's chakra powers and Wolverine's adamantium claws.
X could play the role of a catalyst. For instance, if X is a magical amulet that Logan discovers. He initially wants to use it for his own gain but then realizes that it could be a powerful tool to help the princess save the kingdom. This realization makes him change his attitude towards the princess and they start to work together.