One possible reason could be that the magic used against him is of a very dark and ancient nature that defies the normal healing spells. For example, if it's a curse created by a long - forgotten dark wizard with unique and unbreakable properties.
Madam Pomfrey, the school healer, would be on the front lines. She has experience with treating all kinds of magical maladies among the students at Hogwarts. However, in this fanfiction, she may be stumped by Harry's condition and have to resort to unorthodox methods or seek outside help.
In this fanfiction, perhaps the goblins use their unique magic or potions to heal Harry Potter. Maybe they have some ancient healing arts that are not known to wizards. It could involve a complex ritual where they draw on the power of the earth or their own magical heritage to mend Harry's wounds, whether they are physical or emotional.
One possible plot could be that Harry has a very serious injury from a dark magic attack. Madam Pomfrey uses all her skills and some rare potions to heal him. During the process, Harry might have some vivid dreams or memories related to his past and his parents. As he slowly recovers, he also discovers some new magical abilities that seem to be a side - effect of the intense healing process.
One important goblin could be Griphook. He's a well - known goblin in the Harry Potter series, and in this fanfiction, he might be the main goblin responsible for Harry's healing. He has knowledge of the secrets of Gringotts and could use that knowledge to aid in the healing process.
In some fanfictions, Pomphry might discover a hidden power within Harry while healing him. This could lead to a whole new adventure for Harry as he tries to understand and control this power. It could also change the way he is perceived in the wizarding world. For example, if it's a powerful healing ability, he could start to be seen as a healer as well as a hero. Another plot could be that Pomphry has to deal with interference from dark forces while trying to heal Harry. They might try to stop the healing process to keep Harry weak or to use his injury for their own evil purposes.
Fanfiction.net is also a great place to find such fanfictions. Just search for 'Harry Potter healed' in the search bar, and it will show you a list of relevant stories. However, be aware that the quality may vary, so you might need to read a few to find the ones that really suit your taste.
Well, in some fanfictions, he might be healed by a powerful magical herb that is rarely found. Maybe a character like Hermione goes on a dangerous quest to find it. She uses her extensive knowledge of magic and ancient texts to track it down, and once she gets it, the herb has the power to mend Harry's severe injuries.
One popular 'Harry Potter healed' fanfiction could be 'The Healing of Harry Potter' where the author might explore Harry's emotional and physical healing after all the traumas he faced in the original series. It could show him finding new ways to cope and grow stronger.