Maybe a story where the characters get lost in the black snowstorm and end up in a parallel dimension. In this dimension, they have to face their own doppelgangers and figure out a way to return to their original world. This would involve a lot of self - discovery and conflict.
A plot could involve Black Lightning training a new generation of metahumans. He could open a school or a training facility where he imparts his knowledge and values. This would also bring in new characters and relationships. Or, what if Black Lightning lost his powers temporarily? How would he deal with it? He could rely on his martial arts skills and detective work to still protect the city.
Well, you could write a fanfiction where the House of Black has to face an external threat. Maybe a dark wizard from another family is trying to steal their secrets or undermine their power. The fanfiction could focus on how the members of the House of Black strategize and use their unique skills to defend themselves. Or perhaps a story about a forbidden love within the House of Black, where two members from different branches of the family fall in love, and they have to deal with the strict family rules and traditions that oppose their relationship. Also, a plot could be about a young member of the House of Black who discovers a new form of magic that has been lost in the family for centuries and how they bring it back to glory.
One idea could be exploring a different backstory for a main character in the Black Diaries. For example, if there is a mysterious character, you could write about their childhood and how it led them to be the way they are in the original story. Another plot could be a time - travel scenario, where a character goes back in time to change an important event in the Black Diaries' world.
One idea could be exploring the Black family's history before the events in the original story. Maybe delving into their family secrets or hidden talents.
One idea could be exploring the backstories of the main characters in the Black Shadows world. Maybe there was a tragic event in their past that shaped who they are. Another could be a what - if scenario, like what if a certain character had made a different choice at a crucial moment. It could lead to a completely different story arc.
Perhaps the black wolf is actually a cursed prince and the fanfiction could focus on his journey to break the curse. He might meet a kind-hearted maiden who helps him along the way.
A cool plot for The Black Company fanfiction could be a story about a new recruit who has some special power that no one in the company has ever seen before. This power could either be a great asset or a source of suspicion among the other members. Or you could write a plot where the company has to face an enemy that is not from their usual foes, like a supernatural force that they don't understand at first. It could also be interesting to write a story about the relationships within the company, like a love story between two members that has to be kept a secret because of the company's rules.
Perhaps a fanfiction where the Black Phantom has to infiltrate a high - security facility. They have to use their stealth and unique powers to get past various traps and guards. Along the way, they might discover a dark secret that the facility is hiding, which could be related to their own origin or a greater threat to the world.
A plot could revolve around Narcissa and Sirius in their Hogwarts days. They could be involved in a mystery within the school, like a series of strange disappearances of students. Since they are both from the Black family, they might have some inside knowledge that helps them solve the mystery, and in the process, form an unexpected bond.
One idea could be that the Shadow discovers a hidden power within the Black Knight that could change the fate of their world. Maybe the Black Knight has a connection to an ancient magic that only the Shadow can unlock through their unique bond.