The Last Magicians, a novel by John Jakes.

Cham the Magician, sometimes called Helleyes, was a huge black-haired man with a raven nemed Deth and a runesword that moaned for blood. He was the last of the Red Company, a league of magicians who had fought for freedom and served the good. When the horror of the Unborn, the godhead of evil, was loosed upon the world, Cham was long weary of fighting. He vowed it was not his battle and made ready to sail to the peace of his home in Seastrand… And then he met Debra, of the gray eyes and long shining hair, and Cham knew he must go forward and fight the Unborn, though his strongest spell may break on its monster form.