Well, in the fanfiction, if Harry controls Fiendfyre, it could have a profound impact on his relationships. His friends might be initially worried about him using such dark magic. Hermione, for example, might try to persuade him to stop. But if he can use it for good, like fighting off a horde of dark creatures that are attacking Hogwarts, it could also strengthen his bonds with some of his peers who see the value in his new ability. And from a magical perspective, it could open up new avenues of magical research as wizards try to understand how he is able to control such a dangerous spell.
One consequence could be that he is feared by others. Fiendfyre is a very dangerous and dark magic, so if Harry is seen controlling it, some people in the wizarding world might view him with suspicion and fear, thinking he is turning to the dark side. Another consequence might be that it drains his magical energy a great deal. Controlling such a powerful and volatile spell could take a toll on his magical reserves, leaving him weakened after using it.
The control of Fiendfyre by Harry could lead to a change in the power dynamics in the wizarding world. His new - found ability could make him a target for those who want to use it for their own evil purposes. On the other hand, it could also give him an edge in fighting against dark wizards. However, it might also cause some destruction accidentally. Fiendfyre is hard to fully control, and even a small mistake could lead to large - scale damage to the environment or to people around him.
In some fanfictions, Harry might gain the ability to control Fiendfyre through intense magical training. He could be mentored by a powerful wizard who teaches him the dark arts in a controlled way, allowing him to master Fiendfyre. Another possibility is that he inherits some ancient magic that gives him this power. For example, if he discovers a long - lost family heirloom that has the magic to control such dangerous spells.
One interesting aspect could be the power and danger it represents. Fiendfyre is a very powerful and uncontrollable dark magic. In fanfiction, seeing Harry Potter use it might show his desperation or a new level of his magical abilities. Maybe he uses it to fight a particularly strong enemy that can't be defeated by normal means.
It can create a lot of chaos. Since fiendfyre is so powerful and hard to control, it can quickly turn the story into a high - stakes situation. The narrative might shift from a more typical adventure to a race against time to stop the fiendfyre from spreading out of control.
One consequence could be that it changes the power dynamics in the wizarding world. If Harry can control Fiendfire, he becomes an even more powerful wizard, which might make some people fear or envy him.
One challenge could be the basilisk's own will. Even if Harry has the ability to control it, the basilisk is a powerful and ancient creature with its own instincts. It might resist Harry's control from time to time, especially when it comes to situations that go against its natural behavior, like being made to not attack innocent students.
One consequence could be that it disturbs the balance of the ninja world. The dead are supposed to rest, and by controlling them, Naruto might be messing with the natural order. This could lead to other ninja clans or villages seeing him as a threat.
One consequence could be a change in the school's power structure. If Harry controls Hogwarts, the old hierarchies might be challenged. For example, the influence of some traditionalist teachers could decrease. Another consequence might be a shift in the curriculum. Harry may introduce more practical and combat - related magic lessons, given his own experiences.
On the positive side, he may gain more opportunities to learn advanced magic sooner. This could make him a more powerful wizard in the long run. But he also has to deal with the jealousy of some students. They might think he's getting special treatment, which could lead to some bullying or isolation. Also, the professors might have higher expectations of him, which can be both motivating and nerve - wracking.
In the 'Harry Potter Controls the Elements Fanfic', perhaps Harry discovers his element - controlling powers gradually. He first starts with something simple like controlling the wind to cool himself on a hot day at Hogwarts. Then, as he grows more powerful, he can combine elements. He could create a storm by mixing air and water elements, which he uses to protect his friends from a group of Death Eaters.
He might have enhanced magical perception. Since he can control spacetime, he could be more in tune with the magical energy that flows through different times and spaces. This would allow him to sense things others can't.