A possible plot could be that Voldemort adopts Harry after seeing a prophecy that Harry is the key to saving the wizarding world in a different way than just defeating him. So, Voldemort decides to raise Harry in a way that will make him a powerful ally. They go on adventures together, facing ancient magical threats that neither could face alone, and along the way, they form an unlikely bond.
Yes, there are some fanfictions with this concept. It's an interesting take on the Harry Potter universe as it flips the typical relationship between Harry and Voldemort. In these fanfictions, the story often explores how Voldemort's actions change when he takes on the role of an adoptive figure to Harry, who has been abused. It can lead to some really unique character developments and plot twists.
One popular one might be 'Voldemort's New Heir' where Voldemort discovers Harry's abused situation and decides to take him in for his own purposes. He starts to train Harry in dark magic, but an unexpected bond forms between them.
One common trope is the redemption arc of Voldemort. In these fanfics, he goes from being the evil Dark Lord to a more caring figure. Another is Harry's struggle with his past abuse and how he slowly heals with Voldemort's new - found kindness.
Another option is to ask other Harry Potter fanfiction enthusiasts. You could join some Harry Potter - related forums or groups. There are usually experienced readers who have a wide range of knowledge about different types of fanfictions. They might be able to point you in the right direction and tell you about some great stories with this particular plot.
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.
Harry would be more open to dark magic. Since Voldemort is his adoptive father, he would be exposed to different aspects of magic earlier. He might not have the same fear of the dark side as in the original story. For example, he could be more confident in using spells that are considered dark but for good reasons, like using the Imperius Curse to stop a criminal.
Often, Voldemort starts as this purely evil figure. But when he adopts Harry, he begins to show some unexpected softness. For example, he might start to protect Harry from other threats, which is very different from his usual self.
At first, it would probably be very tense. Harry would be suspicious of Voldemort's motives, and Voldemort would be cautious of Harry's potential to rebel. But as time goes on, they might develop a strange sort of understanding. Harry could start to see Voldemort as more than just a pure evil figure, and Voldemort might start to view Harry as something more than an enemy.
One popular 'Voldemort adopts Fem Harry' fanfiction is 'The Dark Lord's Daughter'. It has an interesting take on how Voldemort's character would change with a daughter figure. Another one could be 'A Different Path for Fem Harry' which explores the magical world from a new perspective with this unique relationship.
One possible plot could be that Harry is magically compelled to submit. Voldemort might use some dark magic or a powerful artifact to control Harry's mind. Another plot could be that Harry submits out of a false belief that it will save his friends. For example, Voldemort could deceive Harry into thinking that if he surrenders, his friends will be spared. Or perhaps Harry is so worn down by the fight that he gives in, thinking there's no other way, and then the story could explore how Voldemort uses Harry's submission to his advantage, like making Harry a tool to gain the loyalty of other wizards.