Perhaps in the fanfiction, the Dark Phoenix is exposed to a new world or dimension where good prevails. This new environment makes her reevaluate her actions and she decides to turn good. For example, she might see how the inhabitants of this place live in harmony and without the chaos she has been causing. This contrast could be the push she needs to change. She could also start to form relationships with the positive characters in this new world, which further encourages her transformation.
Well, in fanfiction, the Dark Phoenix turning good could be a complex and multi - faceted process. It might start with her being exposed to a different ideology, perhaps one of peace and unity. This could make her question her current state of being. Additionally, her powers could be used in a more positive way. For instance, instead of causing destruction, she could use them to heal or protect. The author might also explore her internal struggle between the dark and the good within her, and how she finally overcomes the dark side. This could involve her facing her past traumas and using them as a stepping stone towards becoming a better version of herself.
Perhaps it's due to a psychological breakdown. Batman has endured so much trauma over the years. The constant fight against crime, the loss of loved ones, and the never - ending battle with his inner demons could all take a toll. One day, he just snaps. His mind can no longer handle the pressure, and in an attempt to escape from his own tortured self, he subconsciously adopts the persona of the Joker, as the Joker seems to have no such moral and emotional burdens.
In some fanfiction, it might be related to a hidden magic within Hogwarts itself. There could be a mysterious force in the school that reacts to Harry's unique connection to the place. For example, if he uncovers a long - forgotten chamber or artifact that has some sort of transformative power. Since basilisks are associated with the Chamber of Secrets, it's possible that something in that area could be the cause.
Well, it could be due to a psychic bond. Suppose there's a strong psychic Pokemon or a powerful psychic trainer in the fanfiction. They might form a connection with Biy. Since Espeon is a psychic - type Pokemon, this bond could gradually change Biy's form into that of Espeon. The psychic energy shared between them could be the catalyst for this transformation, which would make for an interesting story arc.
Well, in a fanfiction, it could be due to some sort of magic spell gone wrong. Maybe a villain was trying to defeat Spiderman in a new and unique way and accidentally turned him into a baby. Another possibility is that some strange scientific experiment in the Marvel universe backfired on him.
Another possibility is that it's an accidental result of a powerful magic clash between Voldemort and Harry. When their magic collides in a certain way, it causes an unexpected transformation on Harry, turning him into a girl. This would add a whole new layer of complexity to their relationship and the overall story.
One way it could be plausible is through the use of dark magic manipulation. Voldemort is a master of dark magic. He could perhaps use some form of mind - altering spell on Harry. If he managed to get Harry in a vulnerable state, like when he was feeling isolated or betrayed, the dark magic could seep in and start to change his nature. For example, if Voldemort made Harry believe that his friends at Hogwarts had turned against him, Harry's sense of justice and goodness might be warped, leading him to the dark side.
In some fanfiction, this could happen through a powerful spell gone wrong. Maybe Snape was attempting a complex transfiguration spell for some secret reason, like protecting Harry from a dark magic threat in a very unorthodox way. And the result was Harry being turned into a shifter.
One possibility is that there is an external force at play. For example, an evil entity that wants to disrupt the natural order of things in Forks. This entity manipulates Jacob's wolf abilities and uses Bella as a target. Jacob, not fully understanding what's going on, ends up being the instrument of Bella's transformation. This would create a lot of conflict and drama as Bella has to adapt to her new form and Jacob has to deal with the guilt and consequences.
Another way could be through a potion gone wrong. In the wizarding world, potions can have all sorts of strange effects. If Draco was trying to brew a potion for some other purpose, like trying to gain an advantage in a competition or something, and made a mistake in the ingredients or the brewing process, it could result in him being transformed into Hermione. This would force him to experience life from her perspective, which could be a huge character - development opportunity for him.