The Secret of Sylvia Grindelwald

After Gellert Grindelwald was defeated by Albus Dumbledore, he was imprisoned in Nurmengard, the fortress he had built himself. Later, an Eastern pure-blood witch who admired Grindelwald volunteered to stay at Nurmengard. Many years later, Grindelwald's daughter was born, and the Grindelwald family welcomed a new head once more. But the girl seems to have many secrets, until Dumbledore invites her to become Ravenclaw's deputy head and teach Defense Against the Dark Arts...

There is no fixed male lead in this story. It may have branching storylines. Thank you.