The plot might involve Harry Potter being magically transported to the world where Sparda exists. He would be completely out of his element at first. But then he realizes that there are similarities between the magic in his world and the powers related to Sparda. He teams up with characters from that world and they go on adventures to stop some great evil. He might learn new combat skills from the world of Sparda and bring those skills back to his own world if he ever gets back.
Well, it could be that Harry Potter discovers he has a connection to Sparda. Maybe he has some latent power that is related to Sparda's abilities. He then has to learn to control this new power while still dealing with the threats in his own wizarding world. And perhaps he uses his new - found powers to fight off dark wizards in a more badass way.
Well, it could involve Harry having some of Dante's devil - slaying abilities. Maybe he uses them to fight the dark forces in the wizarding world that Voldemort represents in a more unique way than just magic. For example, he could have enhanced speed and strength like Dante to take on Death Eaters.
Well, it could be that Sparda takes Harry under his wing after seeing the boy's potential and the difficult situation he's in at the Dursleys. Sparda might train Harry in some unique ways, combining magic with his own demon - slaying skills. Harry could learn to be more self - reliant and gain a new perspective on his power.
In a 'Harry Potter Heir of Sparda' fanfiction, the plot might involve a mysterious connection between the wizarding world and the world of Sparda. Harry could be led to an ancient prophecy that links him to the Heir of Sparda. As he delves deeper, he meets characters from the Sparda universe who teach him how to harness his new powers. He then uses these powers not only to defeat Voldemort but also to protect the entire magical world from threats that were previously unknown.
One possible plot could be that a new, extremely powerful and irresistible poison is created by a dark wizard. The main characters, like Harry, Hermione, and Ron, have to find an antidote before it spreads and kills many students at Hogwarts.
Perhaps it's a fanfic that takes the concept of Persephone's abduction in Greek mythology and applies it to the Harry Potter universe. The 'his' could be a dark wizard who kidnaps Persephone, a powerful witch, and the plot could be about her friends in Hogwarts trying to rescue her. Or it could be a more romantic take, where 'his' is a hero - type character and Persephone is in some sort of danger related to the ongoing battle between good and evil in the wizarding world, and he has to save her.
The plot could be about Harry Potter taking a nightly stroll in the Forbidden Forest. He might be feeling restless and decides to explore on his own. During the stroll, he stumbles upon a rare magical creature that he's only read about in books. This encounter could lead to a new adventure as he tries to protect the creature from other threats in the forest.
In a 'Harry Potter is a fighterback in time' fanfic, the plot could involve Harry going back in time for various reasons. It could be to save someone who died in the original timeline, like Sirius Black. He would then have to face the challenges of the past while also trying not to disrupt the future too much. He might also have to deal with the younger versions of his friends and teachers, and how they react to his knowledge from the future. And of course, he would be fighting against the threats of that time period, which could include Death Eaters or other dark wizards. He would need to use his skills and magic in new ways, adapting to the different time and its rules.
Maybe it would involve Harry and his friends having to fight off hordes of zombies in Hogwarts. The Forbidden Forest could be full of zombie creatures.
It could be about the last wizard in the Harry Potter world somehow getting involved with the Marvel universe. Maybe the wizard has to seek help from the Marvel heroes to save the wizarding world from a new and powerful dark force. Or perhaps the wizard brings a unique magic that the Marvel world has never seen before and causes a stir among the superheroes and villains alike.
Maybe in the fanfic, Harry is forced to play the role of a doctor during a wizarding war. He has to quickly learn how to heal the wounded soldiers on the battlefield. This could involve him using his knowledge of magic in innovative ways and also facing moral dilemmas about who to save first. It would be a story full of action and tough decisions.