Another plotline could be their connection to the wider wizarding war. Maybe they have some secret knowledge or a role to play that was not fully explored in the original books. They could be involved in some behind - the - scenes operations during the war, either on the side of the Order of the Phoenix or Voldemort's forces in a more complex way than just being simple followers.
Some fanfics might focus on the sisters' relationships with other female characters in the wizarding world. For instance, how Narcissa's friendship or rivalry with Lily Potter could have developed. Or how Andromeda's choice to marry a Muggle - born affected her relationships with her sisters. These plotlines can add depth to the understanding of the Black Sisters in the Harry Potter universe.
Another possible plotline is that the Sisters Black are outsiders in the wizarding world due to their family's reputation. But they meet Harry, who also has a bit of an outsider status in some ways. Together, they try to change the perception of their families in the wizarding community while also dealing with the normal Hogwarts adventures like Quidditch, classes, and the Forbidden Forest.
One interesting plotline could be the exploration of the Black sisters' relationships before and during the events of the Harry Potter series. For example, how Bellatrix's loyalty to Voldemort affected her relationships with Narcissa and Andromeda. Another could be a story where the sisters have to team up to protect a family secret related to the Black family heritage. Maybe a plot where they interact with Harry Potter in a way that wasn't shown in the original books, like helping him uncover some dark magic that has a connection to the Black family.
A possible plotline could also be the Black sisters' own personal growth and development. They might start off with certain beliefs and values influenced by their family's dark reputation, but as the fanfiction progresses, they could change and become more independent thinkers, perhaps even turning against some of the family's more evil traditions.
Well, perhaps there could be side stories about the unique magical abilities the Sisters Black possess. Maybe one sister has an extraordinary talent for potion - making that she uses to help or hinder the main characters in the Potter universe.
Well, one plotline could be the main character, perhaps a new healer at Hogwarts, dealing with magical maladies that are beyond the usual. For example, they might encounter a spell - induced illness that spreads among the students and has to find a unique cure using both traditional and forgotten healing methods.
Perhaps in the fanfic, Harry is turned into a snake for a period of time. As a snake, he experiences the wizarding world from a different perspective. He has to learn how to survive as a snake while still trying to fulfill his role in the fight against Voldemort. He might encounter other snakes that are either friendly or hostile, and he has to use his wits to deal with them.
Since this is an improper concept for the Harry Potter world, there are no so - called 'good' plotlines in such fanfic. We should uphold the positive values that J.K. Rowling intended in the original work, rather than exploring such unseemly fan - created ideas.
Well, perhaps in 'the king harry potter fanfic', there's a plotline where Harry discovers a long - lost magical artifact that gives him the power and status of a king. This could lead to him having to face off against old enemies who now see him as an even greater threat. And his friends from Hogwarts might have to band together to protect him as he adjusts to this new role. Also, it could involve new magical creatures being drawn to him because of his new - found king - like aura.
A great plotline in some fanfics is the discovery of new spells and magic. It could be that a long - lost spellbook is found, and the characters start to experiment with spells that are more powerful and dangerous than what they are used to. This could lead to all sorts of situations, from accidentally creating new magical disasters to using these spells to fight off new, unexpected enemies.
One interesting plotline could be Voldemort being redeemed. It's a really different take as in the original books he's pure evil. But in fanfic, some writers explore what if he had a change of heart.