There could be a secret about the origin of the Philosopher's Stone in Gringotts. Maybe it was originally created or stored there before it was moved to Hogwarts. Harry's visit could lead to him uncovering this secret, which in turn could change his understanding of alchemy and magic in general. This discovery could also put him in danger as there are many dark wizards who would do anything to get their hands on the knowledge related to the Philosopher's Stone.
He could find a secret about his family's true inheritance. Maybe there are hidden spells or powers that his family has passed down but were kept secret at Gringotts.
Because it can rewrite the story. Fanfiction allows authors to take the basic setting of Harry going to Gringotts and turn it into something completely different. For instance, they can make it so that instead of just retrieving money, he is on a quest to find a magical key that unlocks a powerful spell.
One possible implication could be that Harry has access to unlimited wealth and resources. This would change his status significantly within the wizarding world. He could use the gold to fund various projects, like improving Hogwarts or helping out the less fortunate wizarding families.
It can be important because it might be a key part of uncovering his true identity or heritage in fanfic. Maybe there are things in the vault that will give him more power to fight Voldemort.
It could also be a strategic move. Gringotts is a highly secure place. By buying it, Harry could ensure the safety of important magical artifacts or secrets. He could use it as a base to store and protect things that are crucial for the future of the wizarding world, like ancient spells or prophecies.
One possible motive could be to stop Voldemort from getting his hands on some crucial dark magic item stored in Gringotts. Harry might think that by destroying it, he can prevent Voldemort from getting more power.
Well, in the fanfiction, Fem Harry Potter might find that her vault has been tampered with. Since she's a female, she may be more perceptive to certain details that the male Harry wouldn't notice. She could then start an investigation right there in Gringotts, interrogating the goblins and using her intuition to figure out who was behind the tampering. This could lead to a mystery - solving adventure within the bank.
In this fanfiction, perhaps Voldemort is after some powerful magical artifacts stored in Gringotts. Harry, being the hero, steps in. He might have to face various challenges like dark magic traps and dangerous creatures inside the bank while trying to keep it safe. He could also form an alliance with the goblins, who are initially skeptical of him, but then see his determination to protect their precious bank.
Perhaps in this fanfiction, Harry Potter becomes the King of Gringotts due to some prophecy or a special gift he has. As the king, he could start to reform the goblin - wizard relations. He might introduce new policies in Gringotts that benefit both wizards and goblins, which would lead to a whole new set of adventures and challenges as he tries to balance the different interests.
One possible plot could be that Harry discovers he has some ancient claim to Gringotts. He then has to deal with the goblin politics and power struggles within the bank. Maybe he tries to reform some of the old and unfair practices at Gringotts.
Well, perhaps Harry discovers some major financial mismanagement in Gringotts. Maybe he finds out that the goblins have been embezzling funds or making really bad investments. This could lead to a situation where the bank is on the verge of collapse and Harry, being the hero he is, decides to expose the truth and in the process, bankrupts the bank as all the secrets come to light.