Harry Potter: The Purest Blood

A new student joins Hogwarts as a third year. She's not just any student, though. Her blood is purer than Albus Dumbledore's, purer than Lucius Malfoy's...she is a descendant of Salazar Slytherin, and her surname is proof of that. The Slytherin family went into hiding for thousands of years after Salazar betrayed Hogwarts, eventually hoping the world would forget about the betrayal. They continued to keep the pure bloodline by reproducing in secret, all the way down to Sicily Slytherin and her brother, Thaddeus Slytherin. Thaddeus decided not to attend Hogwarts but instead pursue his own path. Sicily faces many challenges with her lineage, but she meets a boy named Garter Gaunt, and he helps her along.