One way is through distraction. The snake could draw the attention of Harry's attackers away from him. It could slither towards the bad guys and make menacing hisses, causing them to focus on the snake instead of Harry.
Harry might assist in retrieving lost or stolen items. His bravery and problem - solving abilities could come in handy. If a valuable magical artifact was taken from Gringotts, Harry could lead a quest to get it back. He has a knack for getting into and out of difficult situations, which would be useful in such a task.
Another plotline might be that there is a prophecy in the Harry Potter world that only a foreign hero can save Harry. Naruto arrives just in time. He has to learn about the wizarding world quickly while also fending off attacks from the dark side. He could use his shadow clone jutsu to confuse enemies and keep Harry safe.
Perhaps he would name it 'Slyther', as a play on the Slytherin house name. Given that snakes are often associated with the Slytherin house in the Harry Potter universe, it would be a fitting name for his pet snake.
In fanfiction, the consequences can be complex. The snake - based healing might create a bond between the healed person and the snake that has unforeseen implications. For example, they might start to have some snake - like characteristics or instincts. Additionally, the method of using the snake to heal could attract unwanted attention from dark wizards who want to use this power for evil purposes. Harry might then have to protect the knowledge of this healing method and those who have been healed, which could put him in many dangerous situations.
One possible reason could be a dark spell cast on him by a powerful dark wizard. Maybe Voldemort's followers found a new and strange magic to use against Harry. Another reason might be related to some ancient magic that Harry accidentally triggers. For example, he might stumble upon an old, forgotten ritual site and unknowingly activate it, which results in his transformation.
One way could be through meditation. In fanfiction, Harry might have learned some advanced meditation techniques from the Hogwarts library or from a mysterious wizard. By meditating, he can clear his mind and create a mental shield against nightmares.
One scenario could be that there are some dark forces in the fictional multiverse that consider Harry Potter fanfiction a threat to the 'original order'. Percy Jackson, being a hero, steps in. He might have to fight off some shadowy creatures that are sent to burn or erase all the fanfiction. His demigod skills like superhuman strength and his ability to control water would be very useful in this fight. And his loyalty to the idea of creativity and different interpretations (represented by fanfiction) drives him to protect it.
There could be many interesting fanfictions involving Harry Potter and a snake. Maybe the snake is a magical creature with special powers that helps Harry in his adventures. For example, it could lead him to hidden secrets or protect him from dark wizards.
One possibility is that it's a result of a dark curse or spell. Maybe an enemy of Harry has cast a spell on him that causes this strange biological change. Another could be some kind of accidental magic gone wrong. Harry has had his fair share of accidental magic in the original series, and in fanfiction, it could take an extreme form like this.
One common theme is redemption. Slytherins are often seen as the 'bad guys' in the original series, so protecting Harry gives them a chance at redemption. For example, they might be trying to make up for past wrongs or the actions of other Slytherins.