Love and hate are also common. The complex relationship between fem Harry and Voldemort can be filled with both love and hate. It could be a romantic kind of love or a more platonic love - hate relationship. Identity is another theme. Fem Harry may have a different identity in the wizarding world compared to male Harry, and this affects how she deals with Voldemort.
The theme of destiny often pops up. Whether fem Harry is fated to defeat Voldemort or if there's a different path for them both. It's also about the battle between good and evil, but in a more nuanced way as fem Harry's character might bring different perspectives to this age - old battle. For example, she might approach the fight with more compassion or different strategies because of her gender, which in turn affects how the theme of good and evil is explored in relation to Voldemort.
The theme of forbidden love also often appears. Given their status as enemies in the original story, the idea of them having some sort of romantic or deep emotional connection in fanfiction is a popular one. It adds an element of drama and tension to the story.
The theme of trust is often present. Given that Harry and Voldemort are usually enemies, when it's a female Voldemort, the story might focus on how they learn to trust each other or not. And the theme of changing fate. They might try to change the fate that would usually lead to their enmity, for example by working together to prevent a greater evil.
The theme of redemption can also be found. There are stories where Voldemort might be on the path to some form of redemption through his interactions with fem Harry. Also, the idea of forbidden love or a strange attraction sometimes pops up. It's a very different take on the original relationship between Harry and Voldemort. It challenges the traditional view of good and evil. And in some fanfictions, there's the theme of sacrifice. Fem Harry might have to sacrifice something dear to her in order to defeat Voldemort or change his ways.
A frequent theme is the re - imagining of the magical world. With Voldemort in a different role as an adoptive father, the power dynamics in the wizarding world change. Also, the theme of identity is prominent. Fem Harry has to figure out who she is in this new situation where she is associated with Voldemort. And there's often the theme of moral ambiguity as she may be exposed to dark magic yet still hold on to her own sense of right and wrong.
The redemption trope can also be found in some of these fanfictions. Voldemort might start to change his ways because of his relationship with Fem Harry Potter. It's an interesting take as it goes against his established character in the original series. And then there's the trope of the hidden identity. Fem Harry Potter could be hiding her true nature from Voldemort, which adds suspense and mystery to the story.
Power is a common theme. Fanfictions often explore how Voldemort amasses and uses his power, and how others react to it. For example, some stories might show characters trying to resist his power grab.
Well, a major theme is the rediscovery of magic. In the original series, a lot of magic was used in the fight against Voldemort. In these fanfictions, magic can be used for more positive, creative things. Also, friendship is often explored in a different light. Without the dark shadow of Voldemort, friendships can form and develop based on different interests and personalities rather than just being part of a resistance against the Dark Lord.
One common theme could be power dynamics. With Voldemort as Harry's master, there would be a complex play of power, dominance, and submission. Another theme might be redemption. Maybe the story could explore if Harry can somehow redeem Voldemort or if Voldemort can find a different path despite being in a position of power over Harry. Also, identity confusion could be a theme, as Harry has to deal with being under the control of his archenemy in a new and unexpected form.
A frequent theme is the breaking of boundaries. In the original story, Harry and Voldemort are on opposite sides of a huge divide. Fanfictions with this plot explore what happens when those boundaries are shattered. Also, there can be a theme of discovery. Harry discovers a new side to Voldemort that no one else has seen, and this leads to their relationship. And of course, there's the theme of transformation, both for Voldemort in terms of his character and for the whole 'Harry Potter' world view as a result of their relationship.
Well, a frequent theme is the exploration of opposites. Harry is the symbol of good and Voldemort of evil in the original story. In yaoi fanfiction, writers often play with this dichotomy, seeing how these two extreme characters could come together. Also, there's often a theme of secrecy and forbidden love, as their relationship would be frowned upon in the wizarding world.