Maybe in the fanfiction, Sirius Black was framed for a much more heinous crime than he actually committed. He is filled with rage and decides to take revenge on those who wronged him. He uses his knowledge of the wizarding world's secrets and dark magic to create a series of terrifying events. He starts by sending creepy messages to his enemies, like howls that seem to come from inside their own heads. Then he begins to physically manifest in their nightmares, slowly driving them mad with fear.
The plot could involve Sirius Black coming back as a vengeful spirit. After his death, his soul is not at peace. He haunts the halls of Hogwarts, especially the areas that held bad memories for him. Students start to see his apparition, and strange things begin to happen. For example, portraits on the walls start to cry or rooms suddenly become freezing cold. The main character, a young student, decides to find out the truth behind these hauntings and has to face the terrifying Sirius Black's spirit.
A possible plot could be that Sirius Black discovers a new and powerful form of dark magic that corrupts him. He becomes a sort of dark wizard overlord. He starts to gather a group of followers who are also drawn to this dark power. He then sets his sights on Hogwarts, wanting to take over the school. His appearance changes to something more menacing, with his hair turning blacker and his eyes a deep, blood - red. The students and teachers have to band together to fight against this new, terrifying Sirius Black.
One possible plot could be that Sirius Black discovers he has a baby unexpectedly. Maybe it was a result of a past relationship he had before his time in Azkaban. He then has to learn how to be a father while also dealing with the wizarding world's reaction to his new situation, as many might still be suspicious of him.
One possible fanfiction could be set in a dark, abandoned castle where Sirius Black's shadowy figure lurks. His eyes glow menacingly in the dark, and every step he takes makes a creaking noise that sends shivers down the spines of those who hear it. The characters in the story might be a group of young witches and wizards who accidentally stumble upon this place and have to face their fear of Sirius Black.
Maybe Sirius Black gets frustrated with Hermione's know - it - all attitude in the fanfiction. He could be tired of her constantly correcting others or trying to take charge all the time.
Well, the plot could involve Sirius trying to protect his kid from the dark forces that are still after him. Maybe his kid has some special powers, like being able to communicate with magical creatures easily. And Sirius has to teach the kid how to control and use these powers without attracting too much unwanted attention.
One possibility is that Sirius, having finally been vindicated and after the chaos of the war, decides to travel the wizarding world to heal. He might visit old friends and places from his youth that he couldn't before due to his false imprisonment. He could be on a journey of self - discovery, trying to find his place in a world that has changed so much.
One plot idea could be that Sirius Black's daughter discovers her father's true nature and his history through old Hogwarts memories or letters. She might face challenges in the wizarding world because of her father's reputation at first, but then prove herself to be a strong and independent witch. For example, she could be targeted by some Death Eaters' descendants who still hold grudges against Sirius. However, with the help of her friends, she overcomes these difficulties and makes a name for herself in the wizarding community.
In such a fanfiction, perhaps Harry discovers some new evidence that was overlooked. He might find a witness who was too afraid to come forward before. Then he presents this evidence to the Ministry, forcing them to give Sirius a trial.
A great plot could be centered around a prophecy that involves both Nico and Sirius. They are brought together by this prophecy which predicts that only by combining their powers can they save both the demigod and wizarding worlds. Along the way, they have to deal with people who don't trust their alliance, like some of the demigods who think wizards are too different and some wizards who are scared of Nico's connection to the underworld. But they persevere and fulfill the prophecy.
One possible plot twist could be that Sirius Black has a hidden motive for kicking out the Order. Maybe he discovers a traitor within the Order and by kicking them all out, he forces the real traitor to expose themselves in order to rejoin. Another could be that Sirius is being influenced by a dark force that he's unaware of, which is making him act out of character. For example, it could be a spell that was cast on him by a Death Eater.
It might also be a story about a time - traveling character who wishes to change Sirius Black's past but has to keep their intentions hidden. Since time - traveling can have complex consequences, they don't want anyone to know about their wishing, especially when it comes to a well - known and important character like Sirius Black.