In the plot, she could be a link to a part of the wizarding world that Harry has not yet explored. Say she is part of a secret society of witches and wizards. By introducing Harry to this group, it could open up new storylines such as learning new types of magic, getting involved in political intrigue within the wizarding world, or even finding new allies in his battle against Voldemort.
The OC can impact the plot in various ways. He may have knowledge of future events in the original Harry Potter story, so he could try to prevent certain tragedies. For example, if he knew about Sirius Black's fate, he could work towards changing it. Also, his different personality might attract different characters to him, leading to new alliances and rivalries. In some cases, his presence might even lead to a change in Voldemort's plans as he presents an unexpected variable in the wizarding world.
Well, an overpowered OC can act as a catalyst for change. If the OC has the power to time - travel or has some sort of precognition, they can prevent certain disasters from happening. This would mean that events like the death of Sirius Black or Dumbledore could be averted. Their presence also means that the relationships between the main characters in the Harry Potter universe would be different. Harry, for instance, might rely on the OC more than he does on Ron or Hermione in some situations, which would shift the focus of the story and create new story arcs.
Aunt Lemon might also impact Harry's life by introducing him to a different side of the Muggle world. Maybe she has a love for art or music, and through her, Harry discovers these aspects of Muggle culture that he otherwise would have been deprived of. This newfound interest could help him better understand the differences between Muggles and wizards and appreciate both worlds.
Some fanfics have the plot where the OC aunt is an outcast from the wizarding community for some reason. But she overcomes this when she starts to help Harry. She might have been wrongly accused of a crime in the past. As she helps Harry, she also clears her own name. This makes for a very engaging story as there are two parallel storylines of her redemption and Harry's growth. In addition, there are often sub - plotlines about her making new friends and allies in the wizarding world who initially were skeptical of her.
Maybe the aunt is a half - blood who has a foot in both the Muggle and wizarding worlds. She could be an artist who uses magic in her art, creating paintings that come to life. In fanfiction, she could help Harry see that there are different ways to use magic beyond just spells for combat or everyday tasks, and she could also be a source of comfort during his tough times at Hogwarts.
One great 'Harry Potter OC Aunt' fanfiction is 'The Aunt from Afar'. It tells the story of an OC aunt who has magical powers and has been in hiding but resurfaces to protect Harry. She has her own unique backstory and her relationship with Harry is really heart - warming.
Reunions often introduce new storylines. When a long - lost relative is reunited with a character, it might reveal secrets about the character's family history. For instance, if Harry is reunited with a previously unknown relative, it could lead to the discovery of a new magical ability or a long - hidden prophecy. Also, reunions can heal old wounds. If two characters who had a falling out reunite, it can change their relationships and the overall mood of the story.
The 'last will' can also create conflicts. If multiple characters are named in a will, they might fight over the inheritance, whether it's a physical item, a property, or knowledge. This conflict can be between friends or enemies. For example, two houses in the wizarding world might battle over a powerful spellbook left in a will, which then spreads the conflict to other characters and events in the story, greatly affecting the overall plot development.
She could impact the storylines by changing the relationships. For instance, if she befriends Hermione early on, she might encourage Hermione to pursue different areas of study, which could then affect how Hermione helps Harry in later events.
She can create a lot of conflict. For instance, if she's on the dark side, she might be against Harry, which is a huge shift from the original story. This changes the power dynamics and the whole direction of the plot.