Stormqueen! : a Darkover novel

During the lawless Ages of Chaos, when the ruling families of Darkover ruthlessly inbred their laran-gifted offspring to gain powerful talents, a baby was born to the lord of Aldaran. This child, born on a dark and thunder-filled night, was possessed of a terrifying and uncontrolled talent: Dorilys, heiress to her father's domain, could unwittingly call forth lightning, even while still a fretful child. Fearful for his daughter's life and the safety of his domain, Lord Aldaran sent to a tower for help. But even the powers of a trained monitor and a Hastur lord might not be enough to save this painfully afflicted and deadly young woman.