The Craft of Light — Ru Emerson

A WORLD OF MAGICAL ADVENTURE...
...is what three unsuspecting visitors found when they were rudely summoned from their everyday lives by an ancient Thread-wielder. As sorceress, shapeshifter, and soldier, each played a vital role in restoring to the throne Aletto, rightful duke of Zelharri.

THE CRAFT OF LIGHT
Four years have passed, and the three have settled into a comfortable routine. But for Lialla, the outcast duchess of Zelharri, life is a maze of unseen dangers and deadly perils. Her secret powers of Hell-Light are fierce and fearsome; yet they are the very powers that will determine her fate...