There's a fanfic where Voldemort curses the Firebolt, and Harry has to remake it using ancient magic and rare materials. The process is full of challenges and discoveries.
Maybe it's a story where a powerful curse affects the Firebolt, and Harry has to find a way to remake it to regain his edge in Quidditch and face other magical challenges. The focus could be on his determination and ingenuity.
There could be new types of magical creatures that have evolved or been discovered by 2110. Harry might interact with them, and they could either help or hinder his mission.
There could be the Dragonborn. If Harry is in Skyrim, he might cross paths with the Dragonborn, and they could either become friends or rivals depending on the situation.
In this fanfic, Harry is the main focus as he's the one sent to Azkaban. However, other characters would also be important. The guards at Azkaban, the Dementors, would be key figures as they would be the ones constantly menacing Harry. Then there are the Ministry of Magic officials who were involved in sending Harry there. Their motives and actions would be crucial elements in the story.
It could be Voldemort still. Even if Harry and Hermione are sent back in time, Voldemort would still be a major threat. His dark magic and his followers could oppose Harry and Hermione's attempts to change things.
One possible scenario in such a fanfiction could be that Harry is wrongly accused of a serious crime and sent to Azkaban. Snape, who has always had a complex relationship with Harry, might initially believe in his guilt due to their past animosity. However, as the story unfolds, Snape could start to suspect that there is more to the situation. He might begin his own investigation, secretly at first, to find out the truth behind Harry's imprisonment. This could lead to a series of events where Snape has to face his own prejudices and also deal with the political situation in the wizarding world that allowed Harry to be sent to Azkaban so easily.
Well, perhaps Harry could use his magic skills in the world of Skyrim. He might encounter the various races there like the Nords or the Elves and have to adapt his magic to fit the new environment.
Well, in the 'Harry is sent to Azkaban' fanfic, he could discover some dark secrets within the prison. There might be a hidden plot against him or the wizarding world that he uncovers while in Azkaban. And his time there could change his character, making him more cynical or determined to fight the system that wronged him.