The plot might revolve around a conspiracy within the wizarding world. There could be a group that wants to get rid of Harry because of his influence or the prophecy surrounding him. They frame him for a crime that is related to Azkaban, perhaps something to do with a mass breakout attempt that they make it seem Harry was a part of. Once in Azkaban, Harry's mental strength would be tested by the Dementors. Meanwhile, his friends would be using their skills, Hermione's research abilities and Ron's loyalty, to dig up the truth and expose the real villains behind the framing.
In such a fanfiction, the plot might involve false evidence being planted against Harry. Maybe someone uses dark magic to create the illusion that Harry has committed a serious crime, like using an Unforgivable Curse. The Ministry of Magic, being quick to judge, sends him to Azkaban without a proper investigation. Harry would then have to find a way to prove his innocence from within the prison, perhaps with the help of his friends who believe in him and are secretly working on the outside to clear his name.
Well, it could start with a powerful wizard or witch who has a vendetta against Harry. They could manipulate the situation so that it looks like Harry was involved in a dark wizardry incident near Azkaban. The Dementors, being unable to sense the truth due to the framing, would also be a big threat to Harry in Azkaban. His friends like Hermione and Ron would likely be desperate to break him out, but they know they need to find the real culprit first. So they start investigating, following leads that the framer might have left behind accidentally.
In such a fanfiction, perhaps Dumbledore would immediately start an investigation to prove Harry's innocence. He might call in old favors from various magical beings. Hermione would likely be at the forefront of researching ways to break Harry out legally, using her vast knowledge of magical laws.
Maybe a power - hungry wizard in the Ministry of Magic. This person sees Harry as a threat to their own rise to power. They frame Harry to eliminate a rival and at the same time make themselves look like a hero for catching such a 'dangerous' wizard. They could use their position in the Ministry to plant false evidence and manipulate the legal system to send Harry to Azkaban.
If Harry is sent to Azkaban in fanfiction, it would be a huge shock to the wizarding world. In Azkaban, the dark and gloomy environment would take a toll on him. But Harry has a strong will, so he might try to resist the effects of the Dementors. His Gryffindor courage would be put to the ultimate test. And he may discover some secrets about Azkaban while he's there, which could lead to a whole new plotline in the fanfiction.
If Harry Potter were sent to Azkaban in fanfiction, it could be a very dark turn of events. He would likely be wrongly accused, as he often is in the face of Ministry corruption. His time in prison might involve him using his magic in secret to resist the Dementors, and it could also lead to an uprising within Azkaban by other inmates who believe in his innocence. It could also prompt his friends to stage a dangerous rescue mission.
In fanfiction, if Harry Potter were sent to Azkaban, it would be a huge deviation from the original story. He would likely face extreme hardships. The Dementors there would constantly drain his happiness. His friends, like Hermione and Ron, would probably try everything to prove his innocence and break him out. It could also lead to a situation where Voldemort might gain more power without Harry being able to oppose him freely in the wizarding world.
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.
Often, the plot develops with a sense of mystery. His friends would start to investigate what really happened to get him sent there. There would be a search for evidence to prove his innocence. Meanwhile, Harry in Azkaban might discover some dark secrets about the prison itself or about those who sent him there.
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.
A possible plot twist could be that Snape is actually the one who arranged for Harry to be sent to Azkaban, but for a noble reason. Maybe he knew that Harry was in danger from a more powerful dark force and Azkaban was the only place that could keep him safe temporarily. Another twist could be that the real culprit behind the crime Harry is accused of is someone very close to Snape, and Snape has to choose between protecting that person and helping Harry. It could also be that Snape discovers that Harry has a hidden power while in Azkaban that could change the fate of the wizarding world, and he now has to keep Harry alive at all costs.
To survive in Azkaban, Harry would need to keep his mind active. He could recall all his happy memories to counter the Dementors. His knowledge of magic could also be useful. For example, he could try to create some protective spells around his cell. And he might get some unexpected help from the guards or other mysterious forces within the prison.