What could be the possible plot in 'rand joins the black ajah willingly fanfiction'?

Most likely, the leaders of the Black Ajah would be the main antagonists. They would be manipulating Rand for their own ends, perhaps to use his power for some dark ritual or to further their control over the world of the Wheel of Time.

In a fanfiction where Naruto joins the Akatsuki, there could be a lot of interesting character interactions. He would be in close quarters with villains like Sasori or Hidan. Naruto might try to learn more about their pasts and what led them to become members of the Akatsuki. This could also cause a rift in his relationships with his old friends in Konoha. They might see him as a traitor, while Naruto is actually trying to bring about change in the Akatsuki for the greater good.

One possible plot could be that Luke is disillusioned with the Rebellion after some major setbacks. Maybe he discovers some secrets about the Rebellion that make him question their motives. So, he decides to join the Empire in the hope of bringing about change from within. He might start off by using his Jedi skills to gain favor among the Imperial ranks.

In this type of fanfiction, it might also be that Naruto joins Orochimaru to spy on him. The Hidden Leaf Village realizes they need to know Orochimaru's plans from the inside. Naruto, being the brave and somewhat reckless one, volunteers for the mission. He endures Orochimaru's experiments and teachings while secretly sending information back to the village. Eventually, when the time is right, he betrays Orochimaru and uses the knowledge he gained against him.

Well, one possibility is that she gets frustrated with the slow progress of the 'good side'. Maybe she sees all the bureaucracy and inefficiency in the fight against the dark forces and decides that the dark side can offer a more direct way to achieve her goals, like a more efficient magical society. But this would be a huge shift from her original character.

In the fanfiction, Luke could be influenced by his family ties to the dark side. If he discovers some hidden connection to Vader or Palpatine that he didn't know before, it might make him question his place on the light side. He could think that joining the dark side is a way to understand his true heritage better and gain more power to protect those he loves in a different way than the Jedi would allow.

Well, perhaps in this fanfiction, there's a big misunderstanding. Harry might think that by infiltrating the Death Eaters as one of them, he can actually bring them down from the inside. So he pretends to join them, but things get out of hand as he has to constantly prove his loyalty to the dark side, which is really difficult for him.

One plot could be that Naruto is captured by the Sound Village. Instead of being treated as an enemy, they try to convert him. They show him their training methods and how they are building a strong village. Naruto, being the curious and empathetic person he is, starts to understand their motives. He begins to think that by joining them, he can bring about change from within. So, he decides to stay and become part of the Sound Village, while still holding onto some of his Konoha values.

One possible plot could be that Merlin, in his quest to understand the magic that Morgause wields, decides to join her. Maybe he hopes to learn more about his own powers and their origins. Along the way, he discovers secrets about Camelot and his own destiny that he never expected.

Well, one possibility is that Harry is tricked into joining the dark side. Maybe Voldemort uses some dark magic to cloud Harry's mind and make him believe that the dark ways are the right ones. He could start using dark spells and turn against his friends.