Aphrodite can be integrated by having her interfere with the love potions in the Harry Potter world. Since she is the goddess of love, she might have her own take on how love potions should work or might even try to create a more 'authentic' form of love magic. For instance, she could find the existing love potions too artificial and introduce a new kind of potion that is based on true love rather than just infatuation.
She could be integrated as a hidden figure in the wizarding history. Maybe there were ancient wizards who worshiped her and she left some traces of her power in certain magical artifacts. A fanfiction could explore a young wizard or witch discovering one of these artifacts and accidentally summoning Aphrodite or getting in touch with her power. This would then lead to a series of adventures as they try to understand and control this newfound power.
Sabine could be integrated as a foreign exchange student from a magical school in another part of the world. She could bring her own unique set of magical abilities and cultural beliefs related to magic. For example, if she has a different way of casting spells or making potions.
She could be a visitor from another dimension. Arya's skills with a blade and her ability to adapt would be interesting in the context of the magical world. She could form alliances with the characters, like Hermione, and they could learn from each other. For instance, Hermione could teach her magic, and Arya could teach Hermione self - defense without magic.
The Dragon Girl can be integrated as a new student at Hogwarts. She could bring her own set of magical abilities related to dragons, like the ability to communicate with them or use dragon - inspired magic. This would make her stand out among the other students and lead to interesting interactions with the existing characters.
The Wendigo could be a creature that exists in a hidden part of the wizarding world, perhaps deep in the mountains near Hogwarts. Wizards who go astray might encounter it. For example, a group of students on an unauthorized adventure could stumble upon the Wendigo's lair.
One way is to make Krampus a guardian of some sort of ancient magic that is hidden in Hogwarts. The magic has been dormant for years, but with Voldemort's rise and fall, certain dark and light magic has been shifting. Krampus emerges to protect this magic from being misused. Harry and his friends initially see him as a threat but later realize his true purpose and help him in his mission.
The black mage could be an ancient being that was sealed away long ago and is now awakened. In the fanfiction, this mage could have been part of a group that was at war with the founders of Hogwarts. Now that they're free, they seek to destroy the school and all it stands for. The story could focus on how Harry and the others discover the secrets of the founders to find a way to re - seal the black mage.
A water elemental can be introduced as a guardian of a magical spring in the Harry Potter fanfiction. This spring could have special powers like healing or enhancing magical abilities. Harry and his friends might discover it during one of their adventures and have to earn the trust of the water elemental to access the spring's powers.
Powergirl's super strength could be integrated as a form of magic - perhaps she was born with a unique type of magic that gives her physical power far beyond normal wizards. Her flight could be seen as a charm that she has mastered in a different way than traditional broom flying. For example, she could use her flight to quickly reach places in Hogwarts or during battles that are otherwise difficult to access.
The chimera could be a result of a magical experiment gone wrong in a hidden part of Hogwarts. Harry stumbles upon it while exploring the castle's secrets. This discovery could lead to a whole new adventure as he tries to understand the chimera's existence, find a way to control it if it's dangerous, and also uncover the mystery behind the experiment that created it. There could be a connection to a long - forgotten wizard or a secret society within Hogwarts.
Charlie Swan can be integrated as a wizard who has chosen to live in the Muggle world. He could have his own set of magical abilities that are useful in both worlds. For example, he might be really good at spells that can calm wild animals, which would be useful in his job as a sheriff in Forks and also in the wizarding world when dealing with magical beasts.