One of the most interesting characters to include is Nagato. His Rinnegan abilities and his connection to the Sage of Six Paths can create some really complex and exciting storylines in a Sennin Naruto fanfic. He could have some sort of interaction with Naruto's Sage Mode, perhaps teaching Naruto something new about the power of the Sages. Additionally, characters like Gaara can be interesting. His relationship with Naruto and his own unique powers can be incorporated into the fanfic in relation to Naruto's Sage Mode journey.
Jiraiya is also frequently a main character in these fanfics. He's a well - known sennin in the Naruto world. Fanfic writers might explore his past more deeply or create new adventures for him. Another common character is Tsunade. Her relationship with the other sennin and her unique abilities make her an interesting addition to many fanfics.
Another main character could be Kakashi. As Naruto's teacher, he might be involved in the story when the Kitsune Sennin starts to train Naruto. He could be skeptical at first but then come to understand the importance of the Kitsune Sennin's teachings. Also, his own experiences and knowledge could interact with what the Kitsune Sennin brings to the table, adding more depth to the story.
Definitely Naruto himself. His energetic and determined personality would be a great contrast to the often more somber characters in Skyrim. Also, characters like Sasuke could be interesting. His brooding nature and powerful Sharingan abilities would make for some great interactions in Skyrim's dangerous world. And from Skyrim, the Dragonborn would be a must - include. The clash or cooperation between the Dragonborn's Thu'um and Naruto's jutsu would be really exciting to write about.
For the Naruto side, Rock Lee would be really cool. His taijutsu - only fighting style could be really different from what the Halo characters are used to. In Halo, the Arbiter could be an interesting character to include. His story of redemption and his unique combat skills could lead to some great storylines. And of course, Hinata could also be included. Her shy but strong - willed nature could be a nice addition. She might befriend some of the Halo characters and learn new ways to fight from them.
Sasuke is often paired with the Kitsune Sennin in some fanfictions. Since Sasuke is also a powerful ninja, the Kitsune Sennin might see potential in him and try to guide him as well, which could lead to an interesting dynamic between Sasuke and Naruto. Another character is Kakashi. Kakashi's Sharingan and his vast knowledge could interact in interesting ways with the Kitsune Sennin's powers and wisdom. It could create scenarios where they exchange knowledge or team up to train Naruto.
The Sage of Six Paths could be included. As he is the originator of many ninja powers, his connection to Amaterasu could be explored. Maybe he had a hand in creating or containing the power. His presence in the fanfiction would raise the stakes and give a more epic feel. Additionally, Hinata could be in the story. Her love for Naruto could play a role, for example, if Naruto is in danger because of Amaterasu, Hinata could try to save him in her own way.
Sasuke is a great character to include. His cool and brooding personality can create interesting dynamics in crossovers. For example, if he crosses over into the world of Attack on Titan, his skills as a ninja would be put to the test against the Titans. Another interesting character is Kakashi. His laid - back yet highly skilled nature can add humor and action to crossovers. He could be a great addition in a crossover with the world of Inuyasha, sharing his knowledge of combat and jutsu.
Naruto himself is often a popular choice. Fans like to see him go back in time and use his future knowledge and skills to change things. Sasuke is also quite popular. His complex backstory and powerful abilities make for interesting time - travel scenarios. Another popular character is Kakashi. He has a lot of mystery and potential for development in time - travel stories, especially with his Sharingan and his relationship with Obito.
The leaders of different countries can be really interesting characters. They bring in their own political ideologies and leadership styles. For instance, the diplomatic and calm nature of some leaders can contrast with the more fiery and passionate ones. Their interactions could drive the story forward in many ways.
Hashirama Senju is a must - include. His relationship with Tobirama was so complex and important. You could also include Madara Uchiha. The rivalry and grudging respect between the Senju and Uchiha clans were centered around Hashirama and Madara, and Tobirama was right in the middle of it. Another interesting character could be Hiruzen Sarutobi. He was a student of Tobirama, and showing their teacher - student dynamic would be cool.