Often, there's a theme of power corruption. Since Harry has a lot of power in the original series, in these fanfics, his power could lead him down an evil path. Maybe he uses his magic to manipulate others or gain control over the wizarding world in a malicious way. Another theme could be the breakdown of his relationships. His friends might turn against him or he might betray them, which is a big departure from the original story's strong friendships.
One common theme could be a role - reversal in their relationship dynamic. Instead of Spike being the more 'evil' or morally ambiguous one, Buffy takes on that role. Another theme might be how Spike reacts to this new, evil Buffy. It could be about his struggle between his love for her and his sense of right and wrong.
Well, in these fanfics, a common theme is the struggle against the odds. Harry might face challenges like lack of proper tools or difficult customers, but he overcomes them. Also, the theme of growth is present. He starts as a novice perhaps and grows into a skilled mechanic. And sometimes, there's a bit of a mystery involved, like when he has to figure out what's wrong with a particularly tricky car.
A frequent theme is the exploration of the wizarding world's social hierarchy. As a lord, Harry is thrust into a different social stratum. He has to navigate the politics, alliances, and rivalries among the noble families. This often involves dealing with ancient family feuds and forging new relationships. It also includes themes of legacy, as Harry discovers what it means to carry on a family name in a more formal, lordly way.
One common theme is power and privilege. When Harry is nobility, he often has to navigate the power dynamics within the wizarding world's noble families. Another theme is identity. Harry has to figure out how his new noble identity fits in with his existing self - the boy who grew up with the Dursleys.
One common theme is acceptance. In many of these fanfics, Harry's friends learn to accept his autistic traits. Another theme is struggle, as Harry has to deal with the wizarding world which may not always be accommodating to his needs.
One common theme could be how Harry's German heritage affects his relationship with other characters. For instance, it might change the dynamic with Hermione and Ron as they come from different cultural backgrounds.
Common themes often include power dynamics. Since Harry is a demon, he may have new and different powers. Fanfics might explore how he uses or controls these powers, and how they affect his relationships with others like Hermione and Ron. Also, the theme of redemption can be present. Even as a demon, Harry may strive to do good, and the story could be about his journey towards redemption.
One common theme is the power aspect. Since both Harry and Merlin are powerful in their own rights, fanfics often explore how their combined powers would change things. For example, they might be able to defeat dark forces more easily.
In 'Harry is a Slytherin' fanfics, a frequently seen theme is the re - evaluation of Hogwarts houses. Harry's presence in Slytherin makes people question the stereotypes. Family heritage can be a theme too, as Slytherin has a certain reputation related to pure - blood families. Another theme is the forging of new loyalties. Harry has to decide who to trust within Slytherin, which is different from his experiences in Gryffindor. And of course, the theme of personal growth as Harry develops in an environment that is initially foreign to him.
One common theme is power struggle. Harry has to grapple with the power of the Venom symbiote. Another is identity crisis, as he is no longer just Harry Potter but also has this new, alien part of him. And there's often a theme of secrecy too, since he can't just go around showing off his Venom - like powers in the wizarding world.