How does Baba Yaga fit into the Harry Potter fanfiction universe?

One interesting aspect could be Baba Yaga as a hidden character in the Forbidden Forest. Maybe she has a secret lair there and has some connection to the dark creatures. She could be an ancient being that predates Hogwarts and has her own set of magic that is different from what the wizards at Hogwarts use.

Mithril might be incorporated into the fanfiction as a material that has a special connection to certain magical creatures. Maybe unicorns are attracted to Mithril, and a plot could revolve around a group of students trying to use Mithril to lure a unicorn to safety from a poacher. Along the way, they learn more about the magical properties of Mithril and how it interacts with the magic of the unicorn, which in turn could have implications for other areas of magic within the 'Harry Potter' universe.

Freerunning can fit into the Harry Potter universe by adding a new dimension to movement. For example, it can be used for escaping from dark wizards in the narrow alleys of Diagon Alley or Hogsmeade. The characters can use their parkour skills to quickly jump over obstacles and get to safety.

Illumi can fit in as an outsider with unique skills. His combat and stealth abilities are not like anything in the wizarding world, so he could be a wildcard. For instance, in some fanfictions, he might be seen as a new kind of threat or an unexpected ally to the Order of the Phoenix.

In Harry Potter fanfiction, the concept of concubine can be a way to explore different cultural or historical aspects within the wizarding world. It could be used to show a more complex social structure.

Well, in fanfiction, Merlin might be reincarnated in the Harry Potter era. He could retain some of his past memories and powers. As a character, he would bring a different style of magic, one that is more in tune with nature and less structured compared to what the wizards in Harry's world are used to. His arrival could cause a stir among the magical community, with some seeing him as a savior and others as a threat, all while having a special connection with Harry, perhaps as a mentor or a long - lost relative in the magical sense.

Well, in fanfiction, the changling can add an element of mystery. It can be seen as a creature that blurs the lines between the known magical beings in the Harry Potter world. For example, it could be a being that can shift forms like a Metamorphmagus but with different rules and limitations.

Russian royalty can add a new layer of mystery. They might have had their own unique brand of magic that was different from what Harry was used to in the UK. For instance, their magic could be more closely tied to nature, like the freezing winters of Russia.

An amputee character can bring a new perspective. They can use magic to create prostheses or aids. For example, they might use a spell to make a magical limb that can do things normal prostheses can't. This adds a unique element to the magical world.

The Tesseract in Harry Potter fanfiction can be seen as a link between different dimensions in the wizarding world. It could be the key to unlocking secrets about the origin of magic. For example, it might be that the founders of Hogwarts knew about the Tesseract and used its power to build certain parts of the school. Or, it could be that the Tesseract has the ability to break the boundaries between the Muggle world and the wizarding world, creating a whole new set of challenges and adventures for the characters.