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 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!
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 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.
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.
I recommend " Harry Potter: I Am a Legend ", which is an HP Doujinshi novel that is entangled in the name of writing. Hoffa, the protagonist, came to the world of Harry Potter to witness the legend, but he became Voldemort's classmate and Dumbledore's student. The main character has the gift of Transfiguration, from Ravenclaw. The rhythm of the whole article was good, and the battle scenes were wonderful. Although there were some minor problems with logic and character, the original plot was superb. It broke through the framework of the original work, went to school with Voldemort, and was very novel. The characters were deeply portrayed, and the magic battle scenes were far better than the original work. It was a seedling novel worth reading. " Do You Know From the Yuan Family's Bastard Son " was not bad either. It was written by the Duke of Windcloud. When the male protagonist woke up, he became the son of Zhongqin Bo Fu. He thought it was a drama in the inner house palace, but the family was harmonious, so he wanted to be conferred the title of Marquis. However, there were some minor problems such as political drama and the male protagonist's status rising too quickly, but overall, he could be considered a first-class Doujinshi. This Sect Is Going Against the Heavens was a fantasy novel written by Prancing Horse with a Gun. The main character, Lu Xingzhou, had transmigrated into the Great Zhou Dynasty's Founding Martial Saint and the Heaven-Defying Temple's Grand Elder. The sect leader was a reincarnator, and the Grand Elder was a Samsara traveler. The content was rich, and the world structure was not bad. Although there were some shortcomings such as the plot being deliberate and the players not integrating well with the world, it was easy and smart. The words, plot, and logic were all great. The style was humorous, and the early stages were super good. There was also " I Can See the Rate of Return ", an urban novel written by Cowhead Wolf. The male protagonist, Zhang Long, had mutated eyes that could see commercial profits. He was constantly evolving, but there might be a love triangle plot. " Demon Hunting from a Teacher " was a light novel written by Qiu Kong in the north. The male lead, Bai Lutian, had just graduated and became a demon-hunting combat teacher. It was easy and interesting. Harry Potter and the Sorcerer's Stone was not enough. Everyone, please click to read the novel!
Their relationship would be severely damaged. Harry would likely feel betrayed by Sirius. After all, Sirius is supposed to be one of his protectors. It would be a huge breach of trust. Sirius, on the other hand, would probably be filled with guilt if he realizes his mistake. He would have to work hard to regain Harry's trust, if that's even possible in the context of the fanfic.
Sirius could use his knowledge of the wizarding world's secrets. He might know some hidden places or spells that could keep Voldemort at bay. For example, he could put a powerful protective charm on the place where Harry is staying.
Well, if Sirius takes Harry to Voldemort in a fanfic, it would be a huge deviation from the normal story. One possibility is that Sirius is trying to make some sort of deal with Voldemort to save others. But Voldemort is not one to be trusted. Harry, being the Boy Who Lived, is a valuable asset to Voldemort for his own dark purposes. It could lead to a tense stand - off where Harry has to use his own wits and magic, even at such a young age, to try and escape the clutches of the Dark Lord.
In a 'Harry and Sirius join Voldemort' fanfiction, it might start with Voldemort making a very tempting offer. For Harry, it could be something related to saving his friends or family. Sirius might be lured by the idea of protecting Harry in a different way. However, once they join, they would face a moral dilemma. They would have to pretend to be on Voldemort's side while still holding onto their own values. And there would be a lot of internal conflict as they see the evil deeds happening around them.
Some might write it to explore a different side of the characters. It's a way to show how Harry and Sirius could be pushed to their limits and what they would do in extreme situations.