Sapphire

This is your first year in Hogwarts, and you are a muggleborn on the train. This is long after Voldemort was killed (at least 100 yrs) and no one in the books is still alive. However, there is dangerous gang that hates muggleborns, similar to Death Eaters, called Fateborns. Sapphire is a pureblood werewolf, but werewolves are tolerated since there is a potion to stop the aggression (she'll be a harmless wolf on the full moon). You heard a rumor that her mother, an Auror, used to be a Fateborn. In actuality, Sapphire was bit by the werewolf Fateborn called Fang, and her mother switched to avenge that. (You don't know the rest of this, you only heard the first part)