One common theme is self - transformation. The character goes from being a normal human to an alicorn, which often involves a lot of internal and external changes.
It could be an ordinary person, like a young student who was always curious about the magical world of Faust Alicorns. Maybe they accidentally stumbled upon a magic spell or artifact that caused the transformation.
Well, perhaps the human is turned into a Faust Alicorn in a strange accident involving some ancient magic. At first, they are terrified because they look so different. But then they start to discover the beauty and power of being an Alicorn. They could go on a journey to find out why this happened to them, meeting other magical creatures along the way who either help or hinder them in their quest.
One great 'human turned alicorn fanfiction' is 'A New Beginning'. In this story, a human girl finds herself in a magical world and gradually transforms into an alicorn. It's full of adventure and self - discovery.
One popular story could be about a young girl who, through a magical accident, starts to transform into an alicorn. She discovers new powers like flight and magic as she goes through this change, and has to learn to adapt to her new form while hiding it from the non - magical world.
In these fanfictions, a very common theme is adaptation. The human who has become an anthro alicorn has to adapt to a whole new set of physical abilities, like flying and using magic. There's also the theme of cultural shock. Equestria has its own culture, and the new alicorn has to understand and adapt to it. Additionally, the theme of heroism often pops up. As they gain powers, they may be called upon to save Equestria or help its inhabitants, which is a big change from their human life.
You can start by looking on fanfiction platforms like Archive of Our Own (AO3). It has a vast collection of different fanfictions, and you can use the search function to specifically look for 'human turns into alicorn' stories. There are likely to be many different takes on this concept there.
The transformation process itself could be a really interesting part of the fanfiction. It might start with the human experiencing strange glitches in their body, like electrical surges or seeing in infrared. Then, their body would start to change physically, with metal plates emerging from their skin and their internal organs being replaced by Cybertronian components. This transformation could be a painful and confusing experience for the human, but also an exciting one as they discover new powers and abilities that come with their new form.
I'm not sure about a specific title right off the bat. But you can usually find great 'human turns anthro alicorn' MLP fanfictions on websites like Fimfiction.net. Just search for the keywords 'human anthro alicorn' and you'll likely come across some really good ones. You can also check out some MLP fanfiction forums where people might recommend their favorite stories in this genre.
A group of outcasts in the human society could be his allies. They are used to being shunned, so they don't judge Sesshomaru for his past as a demon. They could show him the hidden parts of the human world, like secret passages in the city or places where they can hide from those who would harm them. And together, they could form a sort of family and support system for Sesshomaru.