Themes in 'Harry is a demons mate fanfiction' often include power and its consequences. Since demons are usually associated with power, Harry might gain or be affected by this power in some way. Also, identity is a big theme. Harry has to figure out how being a demon's mate changes his identity as a wizard.
In these fanfictions, a common theme is the exploration of good and evil. Harry is often seen as a 'good' character from the wizarding world, while demons are typically considered 'evil'. The relationship forces both characters and the readers to re - evaluate these concepts. There's also the theme of sacrifice. Sometimes Harry has to sacrifice something from his old life in order to be with the demon, or the demon might sacrifice part of its nature for Harry.
One common theme is the struggle between two different worlds. Harry comes from the wizarding world and the demon from a different, often darker realm. Another theme is the idea of forbidden love, as a relationship between a human - like Harry and a demon is not usually accepted.
One common theme is loyalty. Sirius is extremely loyal to Harry, and vice versa. In many fanfictions, this loyalty is what gets them through tough situations, like when Harry is facing danger from Voldemort.
One common theme is the power dynamic. Since both Harry and Klaus are powerful in their own rights, how they balance that power as mates is often explored.
One common theme is the exploration of a new relationship. Since they come from different fictional worlds, how they get to know and trust each other is often explored. Another theme could be the clash of different magical systems. Harry's magic from the wizarding world and whatever magic or powers Elijah has in his world might interact in interesting ways.
Adventure is also a common theme. Given that both characters are from action - packed universes, many fanfictions will have them embark on quests or battles together. This could involve fighting against dark forces from either the Harry Potter or Lord of the Rings universes, or even new threats created specifically for the fanfiction.
The themes usually include the concept of unity. Harry and Fawkes being mates implies a unity of purpose. They might be on a quest to save the wizarding world together. Another theme is the discovery of hidden powers. Harry might discover new powers through his connection to Fawkes. And of course, there's the theme of friendship. Their relationship is based on a deep friendship that endures through many challenges in the fanfictions.
A major theme is the power of love and how it can change people. Harry, being the main character, has his own set of values and beliefs. When he becomes Severus' mate, they both have to adjust. Their relationship also often explores the theme of breaking boundaries, as their pairing is quite unexpected in the context of the original Harry Potter story. There's also the theme of forgiveness, as Severus has wronged Harry in the past in the original story, and in these fanfictions, they have to work through that.
One common theme is the power dynamic. Bellatrix is a powerful and dark witch, while Harry has his own unique power. How they balance or struggle with this power difference is often explored. Another is redemption. Some stories might have Bellatrix on a path of redemption through her relationship with Harry.
One common theme is the struggle against prejudice. Since Greyback is a werewolf, they often face discrimination, and the fanfictions show how they deal with that while maintaining their relationship.
Well, a frequent theme is the power of love and friendship. Their relationship as mates is seen as a way to overcome the darkness in the wizarding world. Also, there's the theme of self - discovery. Harry and Regulus both learn more about themselves through their bond. For example, Harry might learn more about the Slytherin side of himself through Regulus.
The theme of growth is significant too. Harry and Severus both grow as individuals through their relationship. Harry matures and becomes more understanding of Severus' past actions, and Severus learns to open up and be more vulnerable. And of course, the overarching theme of the mate bond itself, which is often portrayed as a powerful and almost magical connection that binds them together in ways that are both beautiful and challenging.