Warlock by Wilbur Smith
After the death of his beloved Queen Lostris, Taita performs the rites of embalmment and burial for her. Then, stricken with grief, he retreats into the forbidding deserts of North Africa where he becomes a hermit. Over the years that follow he devotes himself to the study of the mysteries of the occult until, armed with these extraordinary powers, he gradually transforms himself into the Warlock. When he is called upon to save the dynasty of Queen Lostris from the clouds of evil that loom over Egypt he discovers that there has, after all, been a divine purpose in his bereavement and suffering . . .