The Lancashire Witches: Harrison Ainsworth

Set in 16th century England. When a Cistercian monk, Borlace Alvetham, is falsely accused of witchcraft and condemned to death by his rival, Brother Paslew, he sells his soul to Satan and escapes. Years later, granted the powers of a warlock, he returns in the guise of Nicholas Demdike to witness Paslew's execution for treason. Dying, Paslew curses Demdike's offspring - who become the 'Lancashire Witches.'  In the 17th century, Mother Demdike, a powerful witch, and her clan face rival witches, raise innocent young Alizon Devi as their own and try to corrupt Alizon despite her innocent ways.