The Cheshire concept can add an element of mystery. It's not a traditional part of the Harry Potter lore, so it can be used to introduce new and unexpected plot twists. For example, a Cheshire - like creature could be the key to unlocking a long - forgotten spell or magic item.
In the context of character development, the Cheshire can act as a catalyst. If a character has an encounter with a Cheshire - like being, it could change their perspective on magic. For instance, a skeptical character might start to believe in more fantastical forms of magic after interacting with this strange and magical Cheshire entity. This encounter could then lead to the character exploring new areas of magic and ultimately growing as a person within the story.
In the context of metahuman fanfiction, Harry Potter works because of the clear divide between those with powers (wizards) and those without (Muggles). The wizards have abilities that are far beyond normal human capabilities, such as the ability to control the elements through magic spells. They also have their own society and rules based on their magical abilities, much like how metahumans in some stories have their own sub - cultures. Moreover, the heroes in Harry Potter, like Harry himself, constantly develop and master their powers, which is a common trope in metahuman stories.
Houdini can fit in as an inspiration for new types of magic. His skills in escape and illusion can be translated into new spells or magical techniques in the Harry Potter universe.
The Sharingan can fit by enhancing a character's perception. In fanfiction, it could make a wizard like Harry more aware of his surroundings during duels. He could see the flow of magic more clearly, similar to how in the Naruto universe, Sharingan users can see chakra.
In Harry Potter fanfiction, the concept of concubine can be a way to explore different cultural or historical aspects within the wizarding world. It could be used to show a more complex social structure.
Well, in fanfiction, the changling can add an element of mystery. It can be seen as a creature that blurs the lines between the known magical beings in the Harry Potter world. For example, it could be a being that can shift forms like a Metamorphmagus but with different rules and limitations.
The concept fits well because the Harry Potter universe already has elements of dark magic. An evil necromancer Harry can be seen as a corruption of his natural magical abilities. He could use necromancy to gain power over others, perhaps even over the Ministry of Magic. This would lead to a power struggle, and his actions would likely have consequences for the entire wizarding community. For instance, he might raise an army of the dead to take over Hogwarts, which would be a major deviation from the normal Hogwarts we know.
The Tesseract in Harry Potter fanfiction can be seen as a link between different dimensions in the wizarding world. It could be the key to unlocking secrets about the origin of magic. For example, it might be that the founders of Hogwarts knew about the Tesseract and used its power to build certain parts of the school. Or, it could be that the Tesseract has the ability to break the boundaries between the Muggle world and the wizarding world, creating a whole new set of challenges and adventures for the characters.
Well, in fanfiction, a succubus can fit into the Harry Potter universe as an otherworldly being. It could be from a different magical realm and end up in Hogwarts. For instance, it might be attracted by the powerful magic there.
In some fanfictions, Atlantean culture could be related to the history of magic in the Harry Potter world. Maybe the ancient Atlanteans were the first to discover magic, and their knowledge has been passed down in fragments over the centuries. Harry might come across an old Atlantean text that reveals secrets about the origin of magic and how it was once more unified across the world before being split into different magical cultures like the ones in Europe.
In fanfiction, the Dragonborn can fit into the Harry Potter universe in various ways. They could be a new student at Hogwarts with their dragon - like abilities being a big secret. Or they might be a mysterious figure from another dimension who comes to help in the fight against Voldemort. For instance, their ability to resist fire could be useful in battles against fire - breathing dragons in the Forbidden Forest.