Magic Steps (The Circle Opens #1‪)‬

Lady Sandrilene fa Toren knows all about unusual magic--she herself spins and weaves it like thread. But when she witnesses a boy dancing a spell, even she is confounded. To her dismay she gets news of a mysterious murderer stalking a clan of local merchants. The killer employs the strangest magic of all: the ability to reduce essence to nothingness. As the murders mount and the killer grows bolder, Sandry's teaching takes on a grave purpose. It becomes clear to everyone that the killings can only be stopped by the combined magic of two people: the young teacher and her even younger student.