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.
The consequences can be far - reaching. Since Harry has a different perspective from the previous administrators, he might make Hogwarts more inclusive. He could open up opportunities for students from all backgrounds, not just the pure - bloods. This could lead to some opposition from the old pure - blood families. Also, in terms of security, he might implement new spells and defenses that are more relevant to the current threats in the wizarding world.
There could be a power struggle within the wizarding world. Some pure - blood families who have long held influence in the Wizengamot might oppose Harry's control. This could lead to internal conflicts, maybe even a split in the wizarding community between those who support Harry and those who don't.
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.
In fanfiction, if Harry controls the Hogwarts wards, it might also change the power dynamics within the school. Teachers and students would have to adjust to this new authority. He could potentially use the wards to create safer areas for students to practice magic without fear of being attacked. This could lead to a more confident and magically proficient student body.
One consequence could be that it alerts all the magical defenses of Hogwarts. This means that every protective spell, charm, and enchantment within the castle would be on high alert. For example, the portraits might become more vigilant, the secret passages might close off more tightly, and the ghosts could be more active in patrolling the corridors.
The Hogwarts community as a whole would be in shock. Harry is sort of a symbol of hope in the fight against the dark forces. His withdrawal could lead to a decrease in morale among the students and teachers, making them more vulnerable to threats. Also, the balance of power within the school could shift, as Harry has often been a key figure in dealing with various dangerous situations.
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.
He might lose the support system he had at Hogwarts. His friends like Ron and Hermione would be separated from him, which could lead to changes in their relationships. They might have to find new ways to communicate and support each other.
One consequence could be that he might get in trouble with the school rules. Hogwarts is a magical place with its own set of traditions and regulations, and a Muggle device like a phone could be seen as an oddity. Teachers might confiscate it thinking it's some sort of strange magical object that could disrupt the magical environment of the school.
One possible consequence could be immediate expulsion. Guns are not part of the magical world of Hogwarts, and bringing such a dangerous Muggle weapon would likely be seen as a serious violation of school rules. Another consequence might be confusion among the students and faculty. They are used to dealing with magic, not firearms. And it could also lead to a breakdown in the magical - Muggle secrecy that the wizarding world tries so hard to maintain, as guns are a very obvious Muggle item.
One consequence could be that his friends start to fear and distrust him. After all, controlling people goes against the principles they uphold. They might see him as a threat and try to stop him, which could lead to a lot of conflict among them.