In this kind of fanfiction, perhaps Harry has a change of heart towards Draco after the war. When he hears that Draco is in Azkaban, he feels a sense of responsibility. Harry could remember some of the good things Draco did during the war, like when Draco didn't identify Harry at Malfoy Manor. So, Harry decides to take matters into his own hands. He might enlist the help of Hermione and Ron, and together they use magic and their wits to break Draco out of Azkaban secretly.
One possible fanfiction could involve Harry finding out that Draco was wrongly imprisoned in Azkaban. Harry might use his influence and his skills as an Auror to dig deeper into Draco's case. He could discover evidence that clears Draco's name, like finding out that Draco was framed by some dark wizards who wanted to get rid of the Malfoy family's influence. Then, Harry would have to fight against the bureaucratic system of the Ministry of Magic to get Draco released.
Well, it could be that there's a new threat emerging in the wizarding world and Harry realizes that Draco has some crucial information. But Draco is in Azkaban. Harry then goes to Azkaban, facing the Dementors. He uses powerful Patronus magic to keep them at bay. Once he reaches Draco, he finds that Draco is in a really bad state. Harry manages to get Draco out and they start working together to face the new threat. Along the way, they also start to understand each other better and form an unlikely alliance.
One consequence could be a change in the public's perception of Hermione. Some might see her as a hero for standing up against an unjust imprisonment, while others might view her actions as traitorous, especially if they believe Draco was truly guilty. This could create a divide among the wizarding community.
He might use the invisibility cloak. Harry could sneak into Azkaban unnoticed and then use magic to break Draco out of his cell. The cloak has served him well in the past, and it would be a simple yet effective way to get past the guards.
One major challenge is the Dementors. They are extremely dangerous and can suck out a person's soul. Harry has to find a way to either avoid them or defeat them. Another challenge could be the security measures in Azkaban. There might be magical locks, guards, and other barriers that he needs to overcome.
One possible plot could be that Harry discovers some new evidence that proves Draco's innocence. Maybe there was a frame - up by some dark forces within the wizarding world. Harry, being the hero he is, feels compelled to act and uses his influence and skills to break Draco out of Azkaban. This could lead to them having to go on the run together, hiding from the authorities while they try to expose the real culprits.
For Harry, his friends in Gryffindor could be a bit confused at first. They know Draco is not exactly a friendly character. But overall, it could lead to a more united front against real threats in Hogwarts. The teachers might also take notice. Dumbledore, for instance, would probably be proud of Harry for showing such selfless courage, regardless of who he was saving.
The plot could start with rumors reaching Harry that Draco is being unjustly treated in Azkaban. Harry, being the hero he is, decides to investigate. He uncovers a conspiracy within the Ministry of Magic that is trying to keep Draco locked up for political reasons. Harry then uses his connections, like his friendship with Neville who now has some influence in the Ministry, to get a hearing for Draco. During the hearing, Harry presents the evidence he has found, which includes magical artifacts that prove Draco's innocence, and Draco is finally released.
He could be doing it out of a sense of justice. Despite his family's views, Draco might see that the way the Dursleys treat Harry is wrong and decides to step in.
The wizarding world would be in shock. The Malfoys are known for their dislike of the Potters, so Draco saving Harry would go against the family's reputation. It could lead to Draco being ostracized by some in the pure - blood community.
It could be that when Harry saves Draco, a hidden prophecy is revealed. The prophecy states that their fates are intertwined and that they must work together to save the wizarding world from a greater evil that is yet to come. This forces them to put aside their differences and grudges and form an unlikely alliance.
One consequence could be that he gains an unexpected ally in Draco. Draco might feel indebted to Harry and start to change his views towards him, which could lead to some interesting interactions between them in the future. This could also cause some tension among their respective groups of friends.