Maybe it's a completely new character created for the fanfiction. This new character could be from a far - off land, with a different kind of magic that Voldemort is interested in. Their marriage could be a way for Voldemort to gain access to that new magic or territory.
One idea could be exploring Voldemort's early years before Hogwarts. Maybe show how his muggle father's abandonment affected him deeply and led to his hatred. Another could be a fanfic where Voldemort tries to redeem himself in some way, which would be a huge twist on his character.
Yes, in the vast world of fanfiction, there are all sorts of wild and creative ideas. Some fans might create a story where Harry Potter is the son of Lord Voldemort for the sake of exploring an extremely different and dark take on the original story. It's a very unconventional concept that goes against the canon, but that's the beauty of fanfic, it allows for such radical re - interpretations.
Lord Voldemort was born Tom Marvolo Riddle. His mother, Merope Gaunt, used a love potion on his father, Tom Riddle Sr. Once she became pregnant and the potion's effect wore off, his father abandoned them. Merope died soon after giving birth, leaving Tom in an orphanage. At Hogwarts, he showed great magical talent but also began to explore the Dark Arts. His hatred for his Muggle father and his desire for power led him to split his soul into multiple Horcruxes, gradually transforming into the evil Lord Voldemort.
Perhaps Harry is tricked. Quirrell could be using some sort of mind - influencing magic or deception. He might make Harry believe that giving him the stone is the only way to save his friends or Hogwarts. Harry, being young and inexperienced, might fall for such a ruse and hand over the stone without fully realizing the consequences.
One possible consequence could be that Voldemort, who is using Quirrell, gains more power. Since the Philosopher's Stone has the ability to create the Elixir of Life, Voldemort could use it to create a new body or regain his full strength much faster. This would put Hogwarts and the entire wizarding world in great danger as Voldemort is extremely powerful and evil. He would likely start to hunt down those who oppose him, especially Harry Potter, with even more vigor.
Focus on Voldemort's emotions. Most often he is portrayed as just evil, but showing his insecurities, his fears, and his desires in a more nuanced way can make your fanfic stand out. For example, his fear of death could be explored in greater depth.
Redemption is also a theme. Many of these fanfictions explore the idea of whether the son can break free from his father's evil and find a way to be good. For example, he might use his power for good instead of evil. This shows the power of choice and the potential for change. It's like a battle between nature and nurture. He has the blood of Voldemort, but can he rise above it? That's what makes these stories so interesting.
I recommend the following novels to you: The Demon Hunter at Hogwarts. The main character was Ethan, the demon hunter. The story of rebuilding the School of Wolves was fantastical and interesting. Professor the Dark Lord at Hogwarts. The male protagonist was Ricardo Silva, the eternal king of werewolves and giants, and the punisher of the sleeping dragon. It was full of dark magic and fantasy elements. In Hogwarts: My Classmate Is Voldemort, the male protagonist was Nelson, who traveled through the chaotic world of Harry Potter. The plot was twisted and unique. I hope you like my recommendation.😗
I can't provide any doujinshi novels about Professor Snape and the Dark Lord because they may violate the terms of use of certain websites. Also, I'm not sure what plot you're referring to when you said that the protagonist was wearing the professor's clothes. If you have any other questions or need answers for other types of novels, please let me know. I will do my best to help you.