A prison guard with a hidden agenda could be an interesting addition. Maybe he's not as loyal to the prison system as he seems and his actions end up affecting the situation of the oc and Prisoner Zero.
You could include a wise old inmate who has been in the prison for a long time and has a lot of knowledge about its secrets. This character could help the oc and Prisoner Zero in their plans.
There could also be a fellow inmate who has a special skill, like being a master of disguise. He could be involved in some of the schemes that the oc and Prisoner Zero come up with, whether it's for getting extra rations or for a more elaborate escape plan.
One idea could be exploring Prisoner Zero's backstory before being imprisoned. Maybe he was wrongly accused and the oc in the fanfic could be on a quest to prove his innocence.
A powerful Raikage - like character as an OC would be great. This character could be extremely strong in physical combat and have a no - nonsense attitude towards protecting Kumogakure.
Terra could be a great addition. He could act as a sort of mentor or a source of conflict. For example, Terra might be initially suspicious of the OC's intentions towards Ventus. Or he could be the one to encourage Ventus to pursue his feelings for the OC, seeing how happy the OC makes Ventus.
You could include characters like Harry Potter. His knowledge of magic from the Hogwarts world would contrast and interact interestingly with Louise's magic from 'zero no tsukaima'. Another good character could be Naruto. His determination and unique ninja skills would add a different dynamic to the story when combined with Saito's swordsmanship.
Survival is a very common theme. The OC prisoner has to find ways to endure the harsh conditions of imprisonment. For example, in many stories, they have to deal with lack of food and water, and hostile captors.
Typically, 'zero tsukiama agnes oc fanfic' might explore different relationships between these characters. It could be romantic, platonic, or adversarial. For example, it might develop a deep friendship between Zero and Agnes that wasn't explored before. Also, the OC (original character) aspect could bring in new storylines and conflicts that revolve around how the OC interacts with Zero, Tsukiama, and Agnes. It might introduce new powers or abilities that the OC has, which then changes the dynamics of the story.
Maybe the OC is a wizard from a different magical culture. For example, he could be from a far - flung wizarding community that was not directly involved in the war but has unique magical abilities. Neville could also be an important character, perhaps collaborating with Harry and the OC on projects to revive the magical plants that were damaged during the war.
There could be Zuko's friends like Sokka or Toph. Sokka might be the voice of reason, trying to give Zuko advice on how to handle the situation. Toph, with her no - nonsense attitude, could offer some blunt but practical insights. Also, Zuko's uncle Iroh could play a significant role. He might be more understanding and supportive, guiding Zuko through this difficult time.
The OC's values are important. If they value loyalty above all else, it will affect how they interact with Tabitha. Maybe they are initially loyal to their own family's magic traditions but as they get to know Tabitha, they start to incorporate some of her ideas. Their hobbies can also be developed. If they like reading old magic books, it can lead to them finding a rare spell that helps Tabitha in a difficult situation.
Seth could be a great addition. His quirky personality could add some humor and unexpected twists to the story. For example, he might accidentally get involved in Marissa and Alex's plans and create chaos in a funny way.