His abilities might adapt to the new environment. His chakra could potentially be influenced by the magic in the peerage's world, maybe evolving into a new form that combines both ninja chakra and magic. His taijutsu skills could be enhanced with the addition of some magical elements for more powerful strikes.
If Naruto joins Serafall's peerage in fanfiction, his abilities would surely change. His rasengan, which is already a powerful attack, could be modified with the infusion of magic. It might become even more destructive or gain new properties like the ability to disrupt magical defenses. His ability to sense danger, which was developed in the ninja world, could be heightened further in the peerage's more dangerous and magical environment. Also, his shadow clone jutsu could be used in new and creative ways, perhaps being able to mimic the abilities of other peerage members or interact with magic in unique ways.
When Naruto joins Serafall's peerage in fanfiction, his abilities would experience significant alterations. For starters, his physical strength, which was built up through ninja training, could be augmented by the magic of the peerage. His speed might also increase in a different way compared to his ninja speed. His ninjutsu would be affected as well. For instance, his fire - style jutsu could potentially become more intense or gain the ability to burn through magical barriers. His ability to communicate with summons might also change, as he could encounter new types of summons in the peerage's world. All in all, his abilities would be a blend of his ninja roots and the new magical elements of the peerage.