Well, King Cold himself would surely be an important character. He could be portrayed as a strict and overbearing father figure, constantly pressuring the OC to be more like him. Frieza could also be a main character, perhaps as a jealous brother who sees the OC as a threat to his own position in the family hierarchy.
There could be a wise old alien mentor who takes the OC under his wing after he is exiled. This mentor could teach the OC about different cultures and values that are contrary to what he learned from his family. Another character could be a powerful bounty hunter who is hired to either kill or capture the OC by his enemies within the family. As the story progresses, the OC and the bounty hunter might develop an unexpected friendship.
Happy could be an interesting character. He could be like a sidekick and a source of comic relief during their relationship journey. For example, he might accidentally interrupt their romantic moments or give Natsu really bad advice on how to court the OC at the beginning. Erza could also be important. She could be the one who gives the OC advice on how to handle Natsu's wild nature, as she has known him for a long time.
One possible plot could be that the OC, as the son of King Cold, struggles to live up to his father's fearsome reputation. He might be conflicted between following in his father's tyrannical footsteps or forging his own path of redemption and justice in the universe.
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 Nurse could be paired with Ruvik. She is a prominent figure in the game's world. A fanfiction could explore a relationship where she either tries to control Ruvik or is influenced by him in unexpected ways, adding a new layer of horror and intrigue to 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.
Superman could also be a main character. He might be the one to first discover the oc after their rebirth. Superman's moral compass would lead him to either protect the oc or keep an eye on them depending on how the oc behaves. And his super strength would be a factor in any interactions with the oc.
Obviously, the oc (original character) who is the son of Batman is a main character. He's likely to be the central focus of the story.
Well, of course, the oc who is the son of Gaea is a main character. There might also be other demigods or mythical beings like centaurs or satyrs that interact with him. Maybe there's a wise old druid who serves as a mentor to the oc, guiding him in understanding his powers.
Well, obviously the OC king is a main character. He's the one around whom the whole story revolves. There might also be his advisors, who could be a mix of old and wise men from established houses, as well as some new faces with fresh ideas. His enemies are also important characters. They could be rival claimants to the throne, or lords who oppose his new ideas for Westeros. And don't forget about the love interest, if there is one. She could be a noble lady from a powerful house, or perhaps a mysterious woman with her own secrets and powers.
Aang could be an ally. Despite the OC being Ozai's son, Aang, with his forgiving nature, might see the potential for good in the OC. He could help the OC to understand the importance of balance and peace.