A believable character arc for Percy could involve him initially struggling with the negative connotations of being associated with Arachne. But as he delves deeper, he realizes that he can use his new status to bring about change. He could learn from the Arachne descendants' resilience and use that to become a stronger leader among the demigods. He might start off as an outcast because of this new identity but end up being respected for his unique perspective and abilities.
First, start with Percy being in denial about his new identity as the son of Arachne. Then gradually have him accept it as he discovers the good aspects of this heritage. For example, the power and loyalty of the Arachne - related demigods.
A believable character also needs to have a goal. In a Percy Jackson Hellsing fanfiction, a character could have the goal of finding a way to combine the powers or knowledge from both worlds. For instance, a demigod might want to learn the secrets of the Hellsing organization's vampire - slaying techniques to use against more powerful Greek monsters. Their actions and decisions throughout the fanfiction should be driven by this goal, which makes them more three - dimensional and believable.
You could have Io start out as being very distrustful of Percy and the demigods. She has been through so much with the gods chasing her that she is wary of any new beings. But as she spends time with Percy and sees his good heart and his determination to help her, she begins to open up. By the end of the fanfiction, she has fully embraced the idea of being part of the demigod world and is ready to fight for its safety, which is a significant transformation for her character.
Connect their existence to the existing lore of the Percy Jackson universe. Maybe their parent is a minor god or goddess that hasn't been explored much. Their powers and abilities should fit within the framework of what we know about demigods and the magical world in Percy Jackson. For example, if their parent is the god of dreams, they might have the ability to enter and manipulate people's dreams.
First, give your character a clear backstory. If they're an SI OC, think about how they ended up in the Percy Jackson world. Were they summoned? Did they fall through a portal? Their backstory should tie into their personality. For example, if they had a tough life before arriving, they might be more cautious or distrustful at first. Also, consider their powers. Make sure they're not overpowered right away. If they have a water - related power, start with basic skills like being able to sense water nearby and gradually develop more complex abilities as the story progresses.
First, give the OC a distinct backstory from their past life. Explain how they died and what their life was like before reincarnation. This will help in shaping their current personality. Second, tie their reincarnation to the Percy Jackson lore. Maybe they were reincarnated because of a curse or a blessing from a god. Third, give them a believable set of powers. Don't make them too overpowered. For example, if they have a power related to water, show how it's different from Percy's power.
First, give your OC a solid backstory. For example, if they're a demigod, think about how they discovered their powers and how their mortal parent dealt with it. If they grew up in a difficult situation, like being bullied for being different, it can add depth. Second, give them a distinct personality. Are they brave like Percy, but also a bit of a loner? Or are they more of a comical character who uses humor to hide their insecurities? Finally, their abilities should fit within the Percy Jackson universe. Don't give them something too overpowered that would break the rules of the world.
Let the characters grow and change through their interactions. If Harry and Percy become friends, Harry could learn about Percy's world and become more open - minded. Percy could also be influenced by Harry's sense of justice. This development in their relationship would make their interactions more engaging and believable.
Develop his relationships. If Percy is the son of Persephone, his relationships with other characters like Annabeth will change. There could be jealousy or confusion from her side as Percy's new heritage might bring new responsibilities and loyalties. Also, his relationship with the gods, especially those related to the Underworld and nature, would need to be explored. He might have to deal with Hades in a different way now.
To create a believable relationship, start with a situation where they are forced to interact, like being thrown together in a dangerous situation. They can start by being cautious of each other, since they come from very different backgrounds. Percy might be wary of Jacob's werewolf nature as it's different from the Greek monsters he's used to, and Jacob might be unsure about Percy's demigod powers.
In developing these characters, consider their backstories more. Percy has his own journey as a demigod, but how does that interact with Arachne? You could create flashbacks where Percy's past experiences with spiders or his mother's influence come into play when he faces Arachne. For Arachne, explore her existence before she became the monster she is. What made her turn against the gods? By delving deeper into these aspects, you can make their characters more three - dimensional in the fanfiction.