Nymphadora Tonks could also be a popular character. She was in a relationship with Remus Lupin in the original series, so fanfiction might explore their relationship further in the context of werewolf mates. And of course, Harry Potter himself might be involved in some way, either as a friend or an accidental mediator in the werewolf - mate relationship.
Remus Lupin is often a central character in such fanfiction. Since he is a werewolf in the original Harry Potter series, it's easy to build stories around him finding a mate. Sirius Black is also sometimes involved, as his relationship with Remus is complex and can add an interesting dynamic to a werewolf - mate story.
Harry Potter himself is also commonly used. His status as the Boy Who Lived can add a lot of drama to the story when he has a demon mate. For instance, his relationship with the demon mate might attract the attention of Voldemort or other dark forces, thinking they can use this relationship to their advantage.
Obviously, Harry Potter is one of the main characters. And for the werewolf, Remus Lupin is a very popular choice as he is a well - known werewolf character in the Harry Potter series.
Luna Lovegood is often reimagined as a female werewolf in some fanfictions. Her unique personality and the way she views the wizarding world adds an interesting twist when she is given the werewolf trait. Writers explore how she copes with her new identity and how it affects her relationships with other characters like Harry and Hermione.
Werewolf mates in fanfiction are also sometimes shown as having a deep connection to nature. Since their transformation is linked to the moon, they might have an affinity for moonlit nights and forested areas. They could use this connection to nature to their advantage, perhaps finding hidden magical places or sensing approaching danger through changes in the natural environment.
One of the popular pairings is Harry Potter and Hermione Granger. Their strong friendship in the original series often gets explored in a romantic way in fanfiction. Another popular one is Draco Malfoy and Harry Potter, which offers a sort of 'enemies - to - lovers' dynamic that many fans find interesting.
One idea could be a werewolf character finding their true mate among the Harry Potter characters. Maybe a werewolf who has always felt like an outcast in the wizarding world finally meets someone who accepts them completely. This could lead to a story of self - discovery and acceptance for both the werewolf and their mate.
Sirius Black is also commonly involved. His relationship with Remus as his friend and his knowledge of Remus' werewolf condition can be delved into deeper. There could be stories about how he helps Remus during difficult times or how their friendship is tested because of Remus' lycanthropy.
One popular one might be 'The Werewolf's Mate' which delves into the complex relationship between a werewolf character and their mate within the Harry Potter universe. It often has elements of the struggle with lycanthropy and the unique bond that mates share.
Harry Potter himself could be a central character. His courage and ability to face dark forces could be put to the test in the Twilight universe. Maybe he has to deal with a vampire coven that has some dark intentions similar to Voldemort.
Since I haven't read it, it's hard to say exactly. But based on the title, Harry Potter and his'mate' who is a god - like figure are likely to be main characters.