Thornlight

"Centuries and centuries ago, the Vale was split in two in a war between witches...The people of the Vale fight it with discs made of lightning; and with an ancient spell. Brier Skystone is the youngest, most talented lightning harvester the Vale's ever seen. Her twin sister, Thorn, is a sensitive artist who's braver than even she knows. And young Queen Celestyna Hightower is determined to be Mender of the Break, the last of her family to bear the weight of anchoring the spell; which is really more of a curse"--Provided by publisher.