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.
The goblin elders who oppose Harry's new - found ownership could be the main antagonists. They might be worried about losing their power and influence within Gringotts to a human, especially one as famous as Harry Potter.
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 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.
In a Fem Harry Potter Gringotts fanfiction, she could be on a mission to steal something from her own vault. Since she's female, she might use her charm and wits in a different way than the original Harry. For example, she could pretend to be a damsel in distress to get past the goblins' security. This would add an interesting twist to the story as it subverts the typical male - hero - steals - item trope.
One popular fanfiction idea could be a story where the Gringotts dragon escapes and forms an unlikely alliance with a young wizard or witch. They might go on adventures together, facing the wrath of the goblins who want their dragon back.
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.
In this fanfiction, perhaps it's not just physical protection. Gringotts could be protecting Harry Potter in a more symbolic or magical sense as well. They might be guarding his family's legacy, which is tied to certain items or secrets in the vaults. This could lead to a whole series of adventures where Harry has to work with the goblins to uncover his true heritage and at the same time, stay alive while being protected by the might of Gringotts.
In some fanfictions, Harry Potter might help Gringotts by using his fame and influence. For example, if there's a threat to the bank's security or reputation, Harry's name could be used to deter villains. His status as the 'Boy Who Lived' makes him a well - known figure in the wizarding world, and his association with Gringotts could bring in more business or protection.
Goblins are essential characters in Gringotts - related fanfiction. They are the ones who run the bank and have their own set of rules and personalities. Some fanfictions might introduce new goblin characters with unique traits. And then there are the dark wizards or witches who could be trying to break into Gringotts for their own nefarious purposes, like Bellatrix Lestrange who had an interest in the Lestrange vault.