A fanfiction could center around Sirius Black's attempts to rescue someone from Voldemort's clutches. He uses his skills as an Animagus and his knowledge of the wizarding world's hidden paths to get close to Voldemort's lair.
One interesting fanfiction idea could be that Sirius Black, after his death, is somehow brought back to life by a powerful magic. He then decides to use this second chance to directly oppose Voldemort. He teams up with other characters, like Hermione and Ron, to come up with a new strategy to defeat the Dark Lord. This could involve exploring new magical theories and spells that were previously unknown.
One possible fanfiction could be about Sirius Black being in a situation where he has to face Voldemort alone. Maybe he discovers a secret weakness of Voldemort that no one else knows. Sirius, with his brave and reckless nature, decides to take advantage of this knowledge to try and take down the Dark Lord once and for all.
Sirius Black was an important positive character in the Harry Potter series, while Voldemort was the main villain. Sirius was a close friend of the Potters and a member of the Order of the Phoenix. He was brave, loyal, and rebellious. James Potter regarded him as a close friend and became Harry Potter's godfather. Voldemort was the leader of the Death Eaters, the pureblood organization of the Extreme Wizards. He was known as the most dangerous Dark Wizard in history. Sirius's cousin, Bellatrix Lestrange, was one of Voldemort's most loyal Death Eaters. Sirius was wrongly imprisoned in Azkaban, escaped from prison and continued to fight Voldemort and his Death Eaters, and eventually died under Bellatrix's Reaper Curse. Voldemort, on the other hand, fought against the forces of justice such as Harry Potter throughout the story. He wanted to rule the Wizarding world, creating many horrors and triggering wars. Harry Potter and the Order of the Phoenix is not enough. Please click to read the novel!
One idea could be that Sirius Black takes his godson on a secret adventure through the Forbidden Forest. They encounter magical creatures and Sirius uses the opportunity to teach his godson about the importance of respecting all forms of magic.
One idea could be that Sirius Black's daughter, who has been hidden away all this time, discovers her true identity while trying to break into Azkaban to clear her father's name. She could have some unique magical abilities that help her in this dangerous quest.
One idea could be that Sirius uses his knowledge of magic from his time as an Animagus and as a member of the Order to quickly heal Hermione's injury. Maybe he transforms into his dog form to track down any threats still lurking around her.
One could also write a fanfiction about Sirius Black's impact on Hogwarts during the events of Prisoner of Azkaban. For instance, his presence, even though he's on the run, could have a big influence on the students. Some students might start to question the Ministry of Magic's actions, and Sirius could inspire them to fight for justice.
It's possible in fanfiction, but it would be a huge departure from his character. Sirius Black is a Gryffindor, known for their courage and loyalty to the side of good. He has personal reasons to hate Voldemort, like the death of his friends at the hands of the Death Eaters. But fanfiction authors might create a complex backstory to justify his joining. Maybe they could write that he was under a powerful spell or was tricked into believing Voldemort had different intentions. Still, it would shock most fans who know the original Sirius.
In the original Harry Potter series, Sirius was not Voldemort. Sirius was Harry Potter's godfather, a Gryffindor graduate, and a righteous adversary to Voldemort. Voldemort, originally named Tom Marvolo Riddle, was a villain who attempted to rule the Wizarding world and committed many evil acts. There might be some special settings in some derivative works or niche interpretation, but according to the orthodox setting of Harry Potter, Sirius and Voldemort were two completely different characters. Harry Potter and the Order of the Phoenix is not enough. Please click to read the novel!
In Harry Potter, there was a derivative pairing of the Fool-wolf, Voldemort x Sirius. However, in the main plot structure of the original novel, Sirius was Harry's godfather, the righteous side against Voldemort, and Voldemort was the villain. They were enemies in the main storyline of the original novel, and this derivative pairing was based on some creation or imagination by fans. Harry Potter and the Order of the Phoenix is not enough. Please click to read the novel!
In a fanfiction, Sirius could have his hair cut by someone else as a sign of trust. For example, he might let a new ally cut his hair, and during the process, they could have a deep conversation about his past, his hopes for the future, and his relationship with Harry. This haircut then becomes a bonding moment between them.