Love and lust are often explored. Given the Veela's alluring nature, there's a lot of tension in the relationship with Harry. Also, the theme of identity. Harry being evil is a departure from his original character, and the Veela mate can either reinforce or challenge this new identity.
One major theme is the struggle for control. The evil Harry Potter may want to control the Veela mate for her powers or beauty, while she may be trying to gain control over his actions to make him less evil. Additionally, the idea of fate and destiny is sometimes present, as if their union is meant to be for some grander purpose in the dark or magical world they inhabit.
I'm not sure of a specific title, but generally in such fanfictions, the Veela mate often brings out different aspects of the evil Harry Potter. Sometimes she tries to tame his evil side, other times she becomes part of his dark plans. You can search on fanfiction platforms using keywords like 'evil Harry Potter' and 'Veela mate' to find some great reads.
One popular idea in such fanfiction could be that the female Veela's allure causes some interesting situations for Harry. For example, it might make his friends act a bit strange around her at first. And Harry would have to deal with the Veela's fiery temperament, which could be a contrast to his more reserved nature. Maybe they meet during a Quidditch match where the Veela is part of a visiting team's fan group.
One common theme is the cultural clash. Since the Veela have their own unique culture, it often clashes with the wizarding world that Harry is from. Another theme is the power dynamic. The Veela usually have certain powers like charm and allure, which can create an interesting power dynamic in the relationship with Harry.
The themes usually revolve around self - discovery. Harry, as a male veela, would need to understand this new aspect of himself. Also, the theme of prejudice can be common. Since veela are a bit of an exotic and not fully understood species in the wizarding world, Harry might face prejudice or误解. And of course, the theme of adventure still persists as he uses his new - found veela - related abilities in his usual adventures, but with a different twist.
One common theme is identity. The OC Veela often has to grapple with her Veela nature while also fitting into the wizarding world. For example, she might have to hide her Veela allure at times.
One common theme is the allure and mystery of the veela. Their beauty and charm are often central, like in many fics where the female veela uses her charm to get what she wants or to influence the characters around her.
One common theme is the exploration of an otherworldly or exotic relationship. Since Veelas are seen as quite different from regular witches and wizards in the Harry Potter world, the fanfiction often focuses on how Harry navigates this unique relationship.
Love and acceptance are common themes. Harry has to accept his mate's vampiric nature, and she has to fit into his world. It's about two different beings coming together.
Well, often there's a theme of protection. Harry, being the central character, might be in a position where he has to protect his veela harem from various threats in the wizarding world. There's also the theme of cultural clash. Veelas have their own culture and traditions, and when they become part of Harry's life, there are bound to be some clashes and reconciliations with the wizarding culture he's used to. Additionally, themes of love and loyalty are quite prevalent as the relationships develop within the harem.
A common theme is self - discovery. Harry, as a female in these fics, has to figure out what it means to have veela inheritance. Another theme is power. Veela powers often bring new abilities that Harry has to learn to control.