First, you need to figure out how to bring the two universes together. Decide on a way for Goku Black to enter the Harry Potter world, like a magical portal or some kind of interdimensional rift. Then, think about how the characters will react to each other. Harry and his friends will be very different from the characters Goku Black is used to. You should also consider the power levels. Goku Black is extremely powerful, so how will the wizards' magic compare? You can start with a simple plot idea, like Goku Black being lost in the wizarding world and needing help to get back home.
To write this kind of fanfiction, start by doing some research on both Harry Potter and Goku Black. Know their personalities, powers, and the rules of their respective universes. For the plot, you could create a situation where Goku Black's arrival in the Harry Potter world disrupts the balance of magic. Maybe his power is so great that it starts to affect the magical ley lines. The Hogwarts professors would be very concerned and try to find a way to control or send him back. Meanwhile, Goku Black might be intrigued by the magic and want to learn more. As you write, make sure to keep the voices of the characters true to their original selves.
His magic might become more physical. Instead of just waving a wand, he could use ki to direct spells. For example, his Patronus charm could be charged with ki energy, making it stronger and more tangible. Maybe his spells would be instant like Goku Black's attacks, no need for long incantations.
Well, one possibility could be that Harry Potter, through some sort of magical accident or powerful spell, gets transformed into Goku Black. He might then use his newfound Saiyan powers along with his wizarding knowledge. For example, he could use magic to enhance his ki blasts or use ki to perform spells in a more powerful way. He might also struggle with the evil tendencies of Goku Black while trying to hold on to his own moral compass as Harry Potter.
It could be a really wild and interesting story. Maybe Goku Black could end up at Hogwarts somehow. He might use his power to either cause chaos or try to take over the wizarding world. And the wizards would have to use their magic in ways they've never thought of to fight him.
Harry's character would become more centered around self - improvement. Goku is always striving to get stronger. So Harry would constantly be looking for ways to improve his magical and physical skills. He might not be as reliant on his friends for support in difficult situations as he is in the original story, instead trying to handle things on his own more often. This could make him seem a bit more independent and self - sufficient.
Well, first you need to have a good understanding of the Harry Potter universe. Know the characters, the magic system, and the settings. Then, come up with an interesting plot idea that fits within that world.
First, you need to have a clear idea of the story you want to tell within the Harry Potter universe. Decide on the main characters and the plot. Also, make sure you know the rules and lore of the series well to stay consistent.
They could exist in the same universe if there was a greater power at play. For example, a powerful being could merge the two universes for a specific purpose. In this new combined universe, Harry would have to adapt to the presence of powerful fighters like Goku. He might use his magic to enhance Goku's powers or create new techniques for him. Goku, in turn, could protect Harry from threats that his magic alone couldn't handle. There could also be a new form of energy that combines magic and ki, which they could both learn to use.
It could be insanely powerful. Goku already has incredible power levels, and Goku Black is no slouch either. When they fuse, it's like combining two nuclear reactors. Their power could be so great that they could effortlessly destroy planets just by flexing their newfound power. They might be able to reach Super Saiyan forms that are far beyond what we've seen in the official series, with power levels that are basically off the scale.
It might be a story where Harry Potter, while exploring different magical texts or spells, stumbles upon a connection to the world of Goku. He starts to study Goku's fighting techniques and tries to incorporate them into his dueling skills. For example, he could learn about Goku's ki control and try to find a magical equivalent in the wizarding world. And he would be constantly in awe of Goku's ability to overcome seemingly impossible odds.
I'd say it's quite unique. Usually, fanfictions tend to stay within the same universe or at least related universes. But Harry Potter and Goku are so different. Harry has his wand and spells, while Goku has his ki blasts and transformations. So when you put them together like this in a fanfiction, it stands out as something different and not very common.