One possible plotline could be that Harry grows up with a very different set of values. Since Lucifer is often associated with rebellion and a certain kind of dark knowledge, Harry might be taught to question authority in a more extreme way than in the original series. He could also have some very unique magical abilities that are influenced by Lucifer's nature, perhaps abilities related to darker forms of magic.
Well, the story might show Harry having a much more conflicted relationship with the wizarding world. Growing up with Lucifer, he may not see the good - evil dichotomy in the same way as other wizards. Maybe he'd try to bring about a new order in the wizarding world, one that blurs the lines between what is considered good and bad magic. He could also have a very different group of friends or allies, those who are attracted to his unorthodox upbringing.
One possible plotline could be Harry struggling to come to terms with his new identity as the Son of Lucifer. He might face internal conflict, wondering if he's doomed to be evil like his supposed father. Another could be the wizarding world's reaction to his revelation. Some might fear him, while others might try to use his power for their own gain.
One possible plotline could be that Harry is raised by a Death Eater in disguise. This would lead to a very different Harry, perhaps one who is more conflicted about his place in the wizarding world and has to grapple with dark magic teachings from an early age.
In some fanfictions, the plot could revolve around Snape teaching Harry about the Dark Arts in a way that Dumbledore never would. Harry might become more proficient in defensive spells against the Dark Arts but also be more exposed to the darker side of magic. This could create a moral dilemma for Harry as he grows up. Additionally, the relationship between Harry and Draco Malfoy could be completely different, as Snape's influence on Harry might make him less likely to be enemies with Draco from the start.
One possible plotline could be Harry using Mycroft's deductive skills to figure out the true nature of his parents' death earlier. He might not trust Dumbledore as blindly and instead start his own investigations.
One possible plotline could be that a new strain of magical typhus breaks out in Hogwarts. The students and teachers have to figure out how to contain it while also dealing with the regular Hogwarts drama. Maybe Hermione tries to research a cure using both magic and Muggle medicine knowledge.
In a 'poison Harry Potter fanfic', a plotline might involve a poisoning attempt on a major character like Dumbledore. This could send the whole wizarding world into chaos as they try to figure out who the culprit is. Harry, Hermione, and Ron would then be on a quest to find out the truth. They might suspect Snape at first, but as they dig deeper, they discover a much more complex conspiracy involving other dark wizards. Another possible plotline could be that a magical poison is used to control the minds of some wizards, and Harry has to break the spell and find the antidote to save his friends and the wizarding world from being taken over by the poison - controlled minions.
A plotline could involve a Zorua being brought to Hogwarts by a new transfer student from a far - off land. This Zorua has special powers that are not fully understood in the wizarding world of Harry Potter. The student is initially shunned because of the strange creature, but Harry and his friends see the potential good in it. As they get to know the Zorua, they discover that it can help them in their fight against Voldemort. Maybe it can create illusions to mislead Death Eaters or use its shape - shifting abilities to infiltrate their ranks.
One possible plotline could be that Harry is cursed and slowly turns into a dragon. As he changes, he has to deal with the physical and mental challenges of this transformation. His friends would try to find a way to reverse the curse while Harry struggles to control his new instincts.
One possible plotline could be Naruto trying to find a way to visit the Harry Potter world. He might search for some kind of magical portal or a powerful spell that can transport him there. Another plotline could be Naruto using the ideas from Harry Potter books to improve his ninja techniques. For example, he could learn about the concept of wandless magic and try to apply it to his chakra control.
One possible plotline could be that Harry has unique magical abilities due to being raised by Death. Maybe he can communicate with the dead more easily and gain knowledge from them that gives him an edge in the wizarding world.