Take JK Rowling's Harry Potter Universe, add Neil Gaiman's Death of the Endless. Okay its not exactly Master Gaiman's Death. But I am not Neil Gaiman, so there is that. This is my version of what Harry Potter and his World would be like if Death was his personal friend, his big sister

Immortal Fangs :

Daywalker with the Silver Fangs

Fandom

Harry Potter

Highlander

Marvel Comics

Era

Hogwarts Year One

Age Rating

Honestly I think this is Teen. But looking at the normal Ratings for Books and Fanfiction, I am going to have to up it to M, due to violence.

Warnings and Alerts

Alternate Universe

Out of Character

BDSM themes

Feudalism 

Vampires

Daywalkers