Well, in many of these fanfictions, a typical plotline involves the chaos that ensues after the marriage law is announced. There are often love triangles or more complex polygons of relationships. Some characters may find themselves in a harem - like situation, having to deal with multiple suitors or partners. And then there's the whole aspect of how the wizarding society reacts to these new relationships. Some may be accepting, while others, especially the more traditional families, might oppose the new pairings strongly.
Harry Potter himself is often a central character. Given his status as the hero of the original series, many fanfictions involve him in these complex marriage law - related relationships. Hermione Granger is also popular, as she's a strong and intelligent character. Her presence in a harem - like situation can lead to interesting relationship dynamics. Draco Malfoy is another one. His complex personality and his family's standing in the wizarding world make him a prime candidate for these types of fan - created relationships.
Another typical character could be Luna Lovegood. Her unique perspective on magic and the wizarding world would be an interesting addition to the harem. She could offer insights and magical solutions that are outside the norm, which would be very useful in a harem situation where they might be facing various challenges, both magical and related to the harem laws.
In Harry Potter fanfiction, the application of marriage law can vary greatly. Some fanfics might follow the wizarding world's own traditional 'rules' of marriage which could be different from Muggle marriage law. For example, there could be magical contracts involved in wizarding marriages that are not present in the Muggle world.
One common theme is the exploration of polyamorous relationships. Since it's a harem - marriage concept, it often involves Harry (or other main characters) navigating multiple romantic relationships at once. Another theme is the cultural clash. For example, how the wizarding world's views on marriage might differ from Muggle concepts when it comes to a harem - style marriage.
Well, sometimes in these fanfictions, a plotline could involve the harem members using their unique laws or magical traditions to help Harry Potter gain more power. For example, if one of the harem members is from a pure - blood family with ancient magical laws, they might use those to give Harry an edge in the fight against the Death Eaters. This can create a whole new dynamic where Harry is not only relying on his own skills and Hogwarts training, but also on the special knowledge and powers of his harem.
One common theme is the struggle against the restrictive marriage law. Female characters often have to fight against the norms set by the law to be with the ones they love.
A very popular pairing is female Harry Potter and Draco Malfoy. The contrast between their personalities and the tension from their past interactions in the original series make for an interesting dynamic in the context of the marriage law. The law might force them together, and they have to learn to live with each other.
One common theme is the struggle against the imposed marriage law. Characters often resist or find it difficult to accept the new rules. Another theme is the discovery of new relationships. Since the marriage law may pair unexpected characters, it leads to exploration of new feelings.
Hermione and Harry are the central figures. However, other characters like Ron also get affected. Ron's relationship with Hermione and Harry is put to the test because of this law. He might feel jealous or left behind. Also, characters like Dumbledore or Snape (if the fanfic includes them in this context) could play roles in either supporting or opposing the law which in turn affects Hermione and Harry.