What are some interesting plot ideas for a 'Harry Potter Demon Butler' fanfiction?

Perhaps Sebastian Michaelis could be summoned by a Hogwarts student who is dabbling in dark magic. He appears in the wizarding world and causes chaos. Harry and his friends suspect something is wrong and start to investigate. Along the way, they discover the existence of demons in a different context than they thought, and they have to use both magic and their wits to deal with Sebastian and the problems he brings.

Perhaps the Demon Prince is actually a long - lost relative of one of the main characters in Harry Potter. This could lead to a complex web of relationships and power struggles within the wizarding world. For example, he might be trying to claim a rightful place in Hogwarts or in the wizarding hierarchy, which would put him at odds with many established characters.

One idea could be Ciel exploring his new demonic powers. He might start to see the world in a completely different way, with his values shifting as he is no longer bound by human limitations. For example, he could use his powers to seek revenge in a more extreme way than he could as a human.

One idea could be that the butler has a secret magical ability that he uses to protect Harry from hidden threats in the wizarding world. Maybe he can turn invisible at will and spy on Harry's enemies.

A fanfiction could revolve around a powerful demon who has been trapped in the wizarding world for centuries. Harry Potter and his friends come across this demon and find out that it holds the key to defeating a new, even greater dark force that is threatening both the wizarding and muggle worlds.

One interesting idea could be exploring how the presence of demon blood affects a character's magic. For example, it might enhance certain dark arts abilities. Another could be the social ostracism the character with demon blood faces within the wizarding world, similar to how half - bloods are sometimes treated in the original series. Also, it might show how the character struggles to control the more primal and dangerous instincts associated with demon blood.

Perhaps the half - wolf demon has a special power that can help Harry Potter in his fight against Voldemort. For example, the demon can sense dark magic from a great distance. They meet in the Forbidden Forest and the demon offers his help to Harry in exchange for protection from the wizarding community's prejudice.

One idea could be a fanfiction where Ciel and the demon, instead of their usual master - servant relationship, become allies in a different realm. They could be on a quest to save a parallel world that is being threatened by a powerful dark force. Another idea is a story where the demon has to protect Ciel from a group of rogue demons who see Ciel as a valuable asset due to his connection with the underworld. Maybe in this fanfiction, Ciel discovers a new power within himself that the demon has to help him control.

One idea could be to create a demon OC who was once a human with a tragic past, like a wronged artist. The OC could have unique demonic powers related to art, such as being able to bring paintings to life in a twisted way. Another idea is a demon OC that is an outcast among demons because they have a sense of morality that is different from the norm in the demon world. They could befriend Ciel in an unexpected way and help him not just for the soul contract but out of genuine care.

One possible plot could be that the butler is actually a wizard in disguise who has been sent to protect Harry. He could use his knowledge of the wizarding and Muggle worlds to keep Harry safe from both magical threats like Death Eaters and Muggle dangers. For example, he could use his connections in the Muggle world to find safe houses for Harry when he needs to hide from Voldemort.