One main theme is friendship. Harry forms new friendships with the unsullied as he helps them. Another theme is redemption. By helping the unsullied, Harry might be seen as redeeming some of the wrongs in the wizarding world. And of course, there's the theme of heroism as Harry steps up to help those in need.
One popular 'Harry Potter helps the unsullied' fanfiction is 'The Aid of Harry Potter'. In it, Harry uses his magic and knowledge to assist the unsullied in various challenges they face in the wizarding world. Another is 'Harry's Unlikely Alliance' which shows how Harry forms a bond with the unsullied and together they overcome dark forces.
The 'harry potter frees the unsullied fanfiction' might be a very unique piece. Given that Harry Potter is often associated with fighting against dark forces and injustice in the original series, in this fanfiction, he could be applying those same principles to the Unsullied. It could explore themes of freedom, heroism, and the power of magic. For example, he might have to outwit powerful enemies who are holding the Unsullied captive, and his friends like Ron and Hermione could also be involved in the mission to free them.
I'm not sure who the author of this fanfiction is. There are so many fanfiction writers out there, and it can be difficult to track down the creator of a specific piece, especially if it's not a widely known one.
One common theme is friendship. Daphne's act of helping Harry often leads to the formation of a strong friendship between them. It shows how two different characters can come together and support each other.
One main way is through his magical knowledge. Harry has learned a great deal during his time at Hogwarts, and this knowledge can be applied to building projects in fanfiction. Another way is his influence. As the Boy Who Lived, he can persuade others to contribute to Hogwarts' development. Also, his courage allows him to take on challenges related to building, like exploring dangerous areas of the castle to find ways to improve it.
Maybe some of the Hogwarts professors like Professor Sprout. After all, she's the Herbology teacher. She could give Harry some expert advice on how to grow different kinds of food plants. She might even let him use some special greenhouses or tools in the school for his food - growing projects.
One common theme is redemption. The idea that Voldemort can be saved or changed through Harry's help. Another theme is the exploration of power dynamics. Since Harry and Voldemort have very different views on power, seeing how they interact when Harry is trying to help can be really interesting.
One possible plot could be that Superman is somehow transported to the wizarding world. He's lost his powers there, and Harry Potter has to help him get back to his own world while also protecting him from the various magical threats in the wizarding world. Along the way, Harry could teach Superman some basic magic to help him defend himself, and Superman could use his strength and heroism in a different way within the magical setting.
One possible plot is that Harry discovers a hidden prophecy that says only by helping Voldemort can he truly save the wizarding world in the long run. So, he reluctantly starts to assist Voldemort in his conquests, all while secretly planning to turn the tables.
The goblin might be helping Harry because Harry once did a favor for the goblin's family. In the fanfiction, the goblin could be an expert in ancient magic spells that have been long forgotten. He could teach Harry these spells, which would give Harry an edge in the fight against the forces of evil. For example, a spell that can turn the dark wizard's own magic back on them.