Snape could also be a character in such a fanfic. His complex relationship with both Harry and Voldemort makes him an interesting addition. He might be in a difficult position, having to keep his cover as a double - agent while also trying to find a way to save Harry without revealing his true intentions to Voldemort.
One possible plotline could be Harry being held captive in one of Voldemort's dark lairs. Voldemort might use the Cruciatus Curse on him repeatedly to try and break his spirit or get information about the Order of the Phoenix. Harry could be isolated and tortured while his friends desperately search for him.
Fanfiction about Voldemort torturing Draco can be quite intense. One possible reason for this plotline is to add more depth to Draco's character. By experiencing such extreme pain and suffering, he may become more sympathetic to the readers. Also, it can highlight the fear that Voldemort instilled in his followers. If he could torture one of his own, no one was truly safe.
I'm not sure if there is such a fanfic. Fanfics cover a wide range of themes and scenarios, but this particular one might be quite rare or even violate some of the general guidelines of the Harry Potter fanfic community. Many fanfic platforms have rules against inappropriate or non - canon - compliant content.
There probably is. Fanfic communities are full of unique and unexpected plot ideas. This kind of plot would completely turn the original story on its head. It might involve some sort of alternate reality where Harry and Voldemort have a common goal or where they are forced to work together due to some external threat. It could be a really interesting read for those who like exploring different interpretations of the Harry Potter universe.
Perhaps Harry is held captive in a hidden location by Voldemort. While being tortured, he has visions of his past and the sacrifices his parents made. This gives him the strength to resist Voldemort's attempts to break his will. His friends then embark on a dangerous quest to find him based on these visions Harry manages to send out magically.
At first, it would be extremely tense and full of suspicion. Harry would be very wary of Voldemort's motives for protecting him. Voldemort, on the other hand, might be impatient with Harry's lack of trust.
Perhaps Voldemort discovers that there is a greater threat out there. In the fanfic, it could be that another dark force is emerging, and Voldemort sees Harry as an ally of sorts against this new threat. So, he decides to protect Harry in order to deal with this common enemy.
At first, it would probably be very tense. Harry would be suspicious of Voldemort's motives, and Voldemort would be cautious of Harry's potential to rebel. But as time goes on, they might develop a strange sort of understanding. Harry could start to see Voldemort as more than just a pure evil figure, and Voldemort might start to view Harry as something more than an enemy.