Well, sometimes the fanfictions might have a plot twist where the Deathly Hallows themselves have different powers than what was originally thought. Maybe the Elder Wand has the power to not only be unbeatable in duels but also to reverse the effects of dark magic, which completely changes the dynamic of the story. This could lead to a situation where characters who were previously doomed by dark magic curses are suddenly cured, and it alters the relationships between the different factions in the wizarding world.
One interesting plot twist could be that a minor character from Hogwarts, like Neville, discovers a hidden power within the Deathly Hallows that was previously unknown. Maybe he realizes that the Elder Wand has the ability to not only transfer power through combat but also through acts of self - sacrifice, which completely changes the way everyone views the power of the Hallows.
Some fanfictions have a plot twist where the Deathly Hallows are actually a test set by the original founders of Hogwarts. Harry finds out that the real purpose of the Hallows was not just to defeat Voldemort but to bring about a new era of magic in the wizarding world. Another plot twist could be that Snape was not actually killed by Nagini but was in a magically induced coma and wakes up at a crucial moment to help Harry. Additionally, a fanfiction might have a twist where the Horcruxes have a connection to the Deathly Hallows, and by destroying the Horcruxes in a certain order, Harry gains new powers related to the Hallows.
A really cool plot twist in some fanfictions is that Harry actually has a long - lost sister. This sister could be hidden away by some powerful magic for her protection. Her appearance in the Deathly Hallows time frame would throw everything into chaos as she might have her own ideas about how to deal with Voldemort and the Deathly Hallows.
A really out - there plot twist in fanfiction could be that the Deathly Hallows themselves have a different origin or purpose than what was originally thought. For example, the Elder Wand might be a key to a whole new realm of magic that Voldemort was unaware of, and Harry uses this knowledge to his advantage in the battle against the Dark Lord.
One interesting plot twist could be Hermione discovering a hidden power within herself related to the Deathly Hallows. Maybe she finds out that she has a special connection to the Elder Wand that no one suspected before.
One interesting plot twist could be that a minor character from the original series turns out to be a key player in the fanfic. For example, a Hogwarts student who was barely noticed before might be revealed as a Death Eater spy all along, adding a whole new layer of mystery and danger to the story.
One interesting fanfiction could be about Draco's role in the search for the Deathly Hallows. Maybe he has a change of heart and decides to help Harry in a secret way. For example, he might use his knowledge of the Dark Arts to counteract some of Voldemort's plans related to the Hallows.
There are fanfictions that look at the post - Deathly Hallows world from the perspective of new characters. For instance, a story about a young witch or wizard who starts at Hogwarts years after the war and discovers some hidden secrets that were left over from the events in the books. Another type of fanfiction could be about the rebuilding of Hogwarts itself. How the school is being renovated and improved, and the stories of the workers and students involved in this process. Some fanfictions also focus on the magical creatures that were affected by the war, like how the centaurs and the house - elves are adapting to the new world order.
The fanfictions can also expand on the theme of power and corruption. The Deathly Hallows represent a great deal of power. Fanfictions may show how different characters are tempted by this power. For instance, Neville could be written as a character who is sorely tempted by the power of the Elder Wand when he has a chance to get it. This shows how the allure of power can change a person, just like it did with some characters in the original story, but in new and different ways.
One interesting fanfiction could be one where Harry and Hermione go on a side quest during the search for Horcruxes. In this story, they might encounter a long - lost magical creature that holds a key to understanding the Deathly Hallows better. It could add a whole new layer of adventure to their journey.