Perhaps an old hermit living in the outskirts of the ninja world. The hermit has a deep knowledge of ancient ninja arts and magic. When he finds Naruto, he decides to train him in these secret arts. Naruto, under his tutelage, becomes a powerful force not just in terms of ninjutsu but also in magic, which was unknown in the normal ninja villages.
A wandering samurai could be his savior. This samurai, having a strong sense of justice, stumbles upon the baby Naruto. He takes Naruto under his wing and teaches him swordsmanship and a different code of honor. Naruto grows up with a unique set of skills and a different perspective on life compared to if he had been raised in the village.
Dumbledore could be a savior in this fanfiction. He has the power and the wisdom to step in and help Harry. He might have been waiting for the right moment to remove Harry from the Dursleys' influence. Also, there could be a new character, like an old and powerful wizard who has been in hiding but senses Harry's distress and comes to his aid. This wizard could have some unique magical abilities that can protect Harry and help him grow into a powerful wizard himself.
One possible plot could be that Naruto is found by a group of outcasts. They decide to raise him away from the Hidden Leaf Village. As he grows, he discovers his own unique powers that are different from the normal ninja skills in the village. He then has to decide whether to return to the village that abandoned him or create his own path with his new family.
Hermione could be a potential savior. She's smart and resourceful. She might figure out where Lockhart has taken Harry by using her vast knowledge of magic and Hogwarts' secrets.
A new student in the school could be the one to save Sakura. This new student might have had similar experiences in their previous school and decides to take a stand against the bullies when they see Sakura being harassed.
His friends from Camp Half - Blood, like Annabeth, Grover, and Tyson, could be the potential saviors. They have always been by his side and would do anything to rescue him.
Perhaps it could be a new character created specifically for the fanfiction. A young ninja from a minor clan who showed extraordinary talent in a unique form of jutsu. But because their clan was small and not very influential, and the larger clans felt threatened by this new talent, they managed to get the village to abandon this prodigy.
There could be a new character, a powerful and kind - hearted witch or wizard who has a premonition about Harry's future. They might decide to step in and save him from the Dursleys. This new character could bring a fresh perspective and new magical abilities to the story as they rescue Harry and take him under their wing.
Hinata could be a great choice. In the original series, she has always had feelings for Naruto. In a fanfiction, they could finally get together more easily. Maybe after the war, Naruto realizes how much Hinata means to him and they start a relationship.
There could be an entirely new character created as a necromancer in Naruto fanfiction. This character could be from a hidden clan that has long been rumored to have necromantic abilities. They could enter the Naruto world and disrupt the balance between life and death, causing all sorts of chaos and new storylines to unfold.
Naruto might interact with Eostia's warriors. They could train together, Naruto showing them his ninja combat skills and them teaching him about Eostia - style combat. There could also be some mysterious characters in Eostia, like an old hermit who has some knowledge about Naruto's sudden appearance in their world and could guide him on his journey in Eostia.