Well, in some fanfictions, Harry might use his advanced magic skills. He could use a combination of powerful healing spells he learned from Hogwarts or perhaps some ancient magic that he discovers. Maybe he has to face some challenges or overcome certain dark forces that were causing the Longbottoms' problems in the first place.
The fanfiction might start with Harry being haunted by the fate of the Longbottoms. He realizes that he has a moral obligation to try and help them. As he begins his journey to heal them, he uncovers secrets about the dark magic that was used against the Longbottoms. These secrets could be related to a particular Death Eater or a forgotten branch of dark magic. Along the way, he has to also deal with his own insecurities and doubts, but with the support of his friends, he perseveres until he finally manages to heal the Longbottoms.
In some fanfictions, Snape might use his advanced knowledge of potions to create a special concoction to heal Harry. He could draw on his skills in Herbology as well to find rare ingredients for the potion.
If Harry was raised by the Longbottoms in fanfiction, his character would be quite different. The Longbottoms are known for their loyalty and their connection to nature. Harry would grow up with a stronger sense of family loyalty, perhaps being more protective of Neville and his family. He would also have a deeper understanding of Herbology, which could influence his problem - solving skills. Instead of being the 'Chosen One' in the typical sense, he might see himself more as part of a family unit that has a role to play in the wizarding world. His self - identity would be less centered around being an orphan and more around being a Longbottom in spirit.
Well, in this fanfiction scenario, Harry would be raised in a different family environment. The Longbottoms, having their own history of struggle against the Dark Arts, would instill in Harry a sense of determination and a different perspective on the fight against Voldemort. His relationship with Neville would be complex yet interesting, as they would share a family bond. And perhaps, his magical education would have a different slant, influenced by the Longbottoms' way of doing things.
Maybe because he has some secret plan or info that makes him think it's the only way to protect them.
Well, in some fanfictions, Harry might use his advanced magic skills he learned from Dumbledore's old books. Maybe he discovers a long - forgotten spell that can reverse the dark magic effects on Lucius.
In some fanfictions, Snape might use his advanced knowledge of potions to brew a special healing elixir for Harry. He could also use his magic skills, like a complex spell specifically designed to mend Harry's wounds, whether they are physical or emotional.
Snape could also use his magical abilities in a more emotional sense. He might share his own past traumas with Harry, creating a bond of understanding that starts to heal Harry's broken spirit. By being vulnerable himself, he shows Harry that it's possible to move past pain.
In fanfiction, it could be that the snake has a symbiotic relationship with a certain type of magic that is beneficial for healing. Harry Potter uses his knowledge of magic and his bond with the snake (through Parseltongue) to tap into this. The snake might be able to detect imbalances in a person's magic or body and then use its own magic to correct them. Harry, understanding this, guides the snake in the process, much like a healer would use a tool or an ingredient in a complex healing ritual.
One reason could be for the greater good of the wizarding world. If Lucius is healed, he might be able to turn away from the Dark side and provide useful information about Voldemort's remaining followers.