It could be Hermione. She's always been smart and resourceful, and she might have found evidence to prove Harry's innocence and get him released.
It could be Sirius Black. Since he has his own experience with Azkaban, he might know some secrets about the place. He could return in some form within the fanfiction and assist Harry in his escape, maybe by leading him through some hidden tunnels or using some special skills he developed during his time in prison.
Well, it could be that when Harry is released from Azkaban, he discovers new magical powers or abilities that he developed during his time there. He might then use these powers to fight against the dark forces that once put him in Azkaban. And he would surely have to deal with the psychological trauma of being in that awful place as he tries to move forward in his life.
Obviously, Harry himself is a key character. His own strength, both physical and mental, could play a role in his release. For instance, he might have developed some new magical abilities during his time in Azkaban that help him break free.
Obviously, Harry Potter himself is a key character as the story is about his release from Azkaban. Dumbledore is likely to be important too. He has the power and influence within the wizarding world to potentially free Harry. His wisdom and knowledge of the situation would play a big role.
One possibility is that Dumbledore discovers new evidence that clears Harry's name. Maybe there was a misused spell by the Ministry that made it seem like Harry was guilty. Dumbledore then uses his influence and magic to break Harry out of Azkaban and they begin to expose the real culprits behind the false accusations.
One possible scenario could be that new evidence is found to prove Harry's innocence. Maybe a powerful magical object reveals the truth about what really happened, leading to his release.
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.
There could be some new characters introduced in the fanfic. Maybe a powerful wizard from a far - off land who has heard of Harry's plight and decides to help. Or perhaps a group of outcasts in the wizarding world who see Harry as a symbol of their own struggle against the unjust system and come to his aid.
It could be Dumbledore. He has great power and knowledge. He might have some secret plan all along. He could use his influence and magic to enter Azkaban and free Harry, especially if he discovers that Harry is wrongly imprisoned.
It could be his friends who are also into the baslik universe. They might have great ideas for the fanfiction and offer their help willingly.