Illumi can fit in as an outsider with unique skills. His combat and stealth abilities are not like anything in the wizarding world, so he could be a wildcard. For instance, in some fanfictions, he might be seen as a new kind of threat or an unexpected ally to the Order of the Phoenix.
One great illumi Harry Potter fanfiction could be 'Illumi in the Wizarding World'. It might explore how Illumi's unique abilities from his original world would interact within the magical setting of Harry Potter. For example, his assassin skills could be pitted against the dark wizards in a really interesting way.
Yes, there could be some. Some fanfiction might focus on a more innocent or platonic relationship within the context of Illumi and a pregnant character, perhaps exploring themes like friendship or family support rather than anything inappropriate.
Friendship or brotherhood is also a big theme. Despite their differences, many fanfictions show how they support each other in their own ways, like Killua relying on Illumi's skills in certain dangerous situations and Illumi having a soft spot for Killua deep down.
In Hisoka x Illumi yaoi fanfictions, the attraction between them could be based on mutual respect for each other's power. Hisoka is always seeking strong opponents, and Illumi is a very powerful assassin. Their interactions in the original work provide a rich source of material for fanfiction writers to develop romantic or at least deeply emotional relationships between them.
Love and loyalty are themes that are often explored as well. It's not always romantic love, but a deep, unwavering loyalty that might exist between them. Some fanfictions show how, despite their differences, they would still be there for each other in difficult situations, like when facing a common enemy or dealing with the challenges within their family.
One interesting fanfiction could be about Killua and Illumi's relationship evolving. Maybe Killua is trying to break free from Illumi's over - protective and controlling ways. They could end up having a heart - to - heart conversation where Killua makes Illumi understand that he needs to grow on his own terms.
One popular trope is the 'enemies - to - lovers' scenario. Given their somewhat antagonistic relationship in the original story, it's a natural progression in fanfiction. Another is the 'forced proximity' trope, perhaps they are forced to work together on a mission, which then leads to the development of their relationship.
One idea could be an Illumi crossover with the Harry Potter universe. Illumi could be a dark wizard from a far - off land who comes to Hogwarts to study the magic there in his own twisted way. He might be intrigued by the concept of the Deathly Hallows and try to obtain them for his own purposes.
It's not a common type. In the vast world of Harry Potter fanfiction, you'll find a lot more stories about Hogwarts during different eras, the relationships between the main trio, or the exploration of the wizarding world's politics. 'Breeder fanfiction' is more of a specialized sub - genre that only a small subset of fans might be interested in, as it delves into family - building and genetic - like concepts which are not as central to the general appeal of the Harry Potter series.