Obviously, Naruto and Alduin would be the main characters. Naruto is the one being raised, so his growth and development under Alduin's influence would be central. Alduin, on the other hand, is the one doing the raising. His motives, his power, and his relationship with Naruto would be key aspects of the story.
It's possible that there could be some original characters created for this fanfiction as well. Maybe Alduin has some minions or allies in this new world that he brings with him or creates. These characters could also play important roles in Naruto's upbringing, either helping Alduin in his task or trying to undermine it depending on their own motives and loyalties.
Naruto and Sheogorath are the two most likely main characters. But there could also be appearances from some of Naruto's original friends like Sasuke and Sakura, though their relationships with Naruto would be very different. They might be more like outsiders looking in on Naruto's strange new life under Sheogorath's influence. Also, characters from the Sheogorath's world might make an appearance in the fanfiction, further complicating Naruto's life and the overall story.
Obviously, Naruto and Erza would interact a great deal. Naruto would also probably interact with Erza's friends from Fairy Tail. He might meet Natsu and they could have some interesting battles or friendly competitions. He could also interact with Lucy, and perhaps learn about celestial spirits from her.
Obviously Naruto is one of the main characters. And Alduin, of course. There might also be characters like Sasuke in Naruto's world who could get involved in the story. In Alduin's world, there could be dragon followers or powerful mages who interact with Naruto and Alduin.
Dumbledore could be another character. He is extremely powerful and wise. He might have some prior knowledge or intuition about Alduin's existence. He could interact with Alduin in a more diplomatic way, trying to understand Alduin's motives and perhaps find a way to co - exist peacefully if possible. Or, if Alduin proves to be a threat, Dumbledore would be one of the few who could stand up to him.
Obviously, Naruto and Erza would be the main characters. Naruto is the young ninja with a lot of potential and a big heart. Erza is the strong and capable character who takes on the role of raising Naruto. There might also be other characters from Naruto's world or Erza's world that make appearances, like Naruto's friends from Konoha in cameo roles, or Erza's guildmates who interact with Naruto as he grows up.
Harry for sure. Then there could be his samurai mentors. Maybe there would also be some characters from the original Harry Potter world who interact with him in this new samurai - influenced life. For example, Hermione might visit him in the samurai village and be amazed at the new skills he has learned.
Well, Harry is the central figure in this fanfiction idea. Since he is being raised by Hidan, Hidan becomes a crucial character too. Then, there could be characters like Hermione. She might be either very intrigued or very concerned about Harry's new upbringing. And of course, there could be antagonists from both universes. In the Harry Potter world, Voldemort or his followers could still be a threat, and in Hidan's world, there might be some enemies that could cross over into Harry's life in this fanfiction.
Obviously, Ash and Arceus are the main characters. Ash is the one being raised, and Arceus is the one doing the raising. But there could also be other Pokémon that are important in Ash's upbringing, like the Pokémon that Arceus assigns to look after Ash or be his companions during his growth.
Obviously, Percy would be one of the main characters. Chaos, who raises him, would also be very important. There might also be some other primordial beings that interact with Percy during his upbringing.
Hades himself would be a central character. His influence on Mal, his parenting style, and his own motives for raising Mal would be important aspects of the story.