Well, it depends on how it's done. If the fanfiction writer is skilled, they could create an amazing story. They could use the concept of Necromorphs to introduce a new kind of dark magic in the Harry Potter world. For example, imagine if Voldemort got his hands on Necromorph - creating magic. However, it could also go wrong if not done carefully. The two universes have different fan bases and expectations, so some fans of either might not like the combination.
The combination of Naruto and necromorphs is unique because it merges two very different genres. Naruto is about ninjas, friendship, and a coming - of - age story in a feudal - like world. Necromorphs, on the other hand, are from a horror genre, all about grotesque body horror and survival. When you put them together in fanfiction, it creates a whole new kind of story that can be both exciting and unexpected.
One way is to focus on the common elements. Both universes have elements of the unknown and the dangerous. In Harry Potter, there are dark wizards and dangerous creatures. With Necromorphs, it's all about the horror of the undead. By highlighting these similarities, the fanfiction can draw in both sets of fans. For example, a story could be about a joint mission between Hogwarts students and some survivors from a Necromorph - infested world to fight a common enemy that combines dark magic and Necromorph - like powers.
The worlds might blend through the use of shared magical elements. For instance, both have magical creatures. The gargoyles' ability to turn to stone during the day and come alive at night could be related to some form of Transfiguration magic in the Harry Potter world.
The themes blend by pitting the light - hearted and somewhat familiar magic of Harry Potter against the mind - bending, incomprehensible horror of Cthulhu. For instance, the concept of good vs. evil in Harry Potter takes on a new dimension when faced with the amorality of Cthulhu - like beings. The wizards' sense of order and their magical laws are challenged when these chaotic and eldritch forces enter their world.
Well, in some fanfics, the honor code of the Yautja might blend with the Gryffindor's sense of bravery. A Yautja might respect a Gryffindor who shows great courage in the face of danger, just as they respect worthy opponents in their own culture.
In these fanfictions, they blend by sharing certain characteristics. For example, the loyalty and camaraderie among the characters in both universes are emphasized. In Harry Potter, it's the loyalty among the students of Hogwarts and the Order of Phoenix. In Kancolle, it's the bond between the shipgirls. This common trait can be a basis for the two universes to interact, like the shipgirls and the wizards/witches working together based on mutual trust.
In 'Harry Potter Incubus Yaoi' fanfiction, it often blends by inserting the concept of incubus (a type of demon) into the Harry Potter universe. The yaoi aspect might come in through male - male relationships. For example, an incubus character could be introduced into Hogwarts and form a relationship with a male character from the original series, thus combining the magical world of Harry Potter with the otherworldly and often sexualized nature of incubus and the male - male relationship dynamic of yaoi.
Well, it often has Harry using Hitman - like skills. For example, stealth and precise attacks. In some fanfics, he might use magic to enhance these skills. Like using a silencing charm while sneaking up on an enemy, just like a hitman would use his training to be quiet.
In fanfiction, the two universes blend in multiple ways. The characters from Harry Potter can be put into Creepypasta - like situations. For instance, Harry might find himself in a situation where he has to face a entity that is not from the wizarding world but from a Creepypasta realm and has to use his magic in a new and untested way to survive. Also, the magic in Harry Potter can be warped to fit the spooky nature of Creepypasta. Spells could have unexpected and disturbing side - effects that are more in line with Creepypasta. The creatures in Harry Potter can also be made more menacing by borrowing elements from Creepypasta. For example, a Hippogriff could be made to look more like a nightmarish beast with Creepypasta - inspired features.
Authors need to first understand the core elements of both universes. For Harry Potter, it's the magic, Hogwarts, and the fight against Voldemort. In KHR, it's the Mafia families and the growth of Tsuna. Then, they can start by introducing characters from one universe into the other in a believable way. For instance, if Harry were to enter the KHR world, how would he adapt to the different rules and powers there?