Robert the Devil (Latin: Robertus Diabolus) is a legend of medieval origin about a Norman knight who discovers he is the son of Satan. His mother, despairing of heaven's aid in order to obtain a son, had asked for help from the devil. Robert's satanic instincts propel him into a violent and sinful life, but he eventually overcomes them to achieve repentance.
It is not known whether or not the legend is based on the life of a real individual. It originated in France in the 13th century and has since provided the basis for many literary and dramatic works, most notably the Meyerbeer opera Robert le diable.
The 19th century Italian writer Arturo Graf gives this version of the legend in his 1889 book Il Diavolo :
There was once a duchess of Normandy who was tormented with a desire to have children and yet could have none. Weary of recommending herself to God, who will not listen to her, she betakes herself to the Devil, and her wish is speedily satisfied. A son is born to her, a veritable firebrand. As an infant, he bites his nurse and tears out her hair; as a lad, he knifes his teachers; at the age of twenty, he becomes a bandit chief. He is dubbed knight, in the belief that thus the wicked instincts raging within him may be overcome; but thereafter he is worse than he was before. No one surpasses him in strength or in courage. In a tourney he overthrows and slays thirty opponents; then he goes roaming about the world; then he returns to his native land, and begins once more to play the bandit, robbing, burning, murdering, ravishing. One day, after cutting the throats of all the nuns of a certain abbey, he remembers his mother and goes in search of her. Soon as they spy him, the servants take to their heels, scattering in all directions; not one tarries to ask him whence he comes or what he desires. Then, for the first time in his life, Robert is astounded at the horror which he inspires in his fellow-beings; for the first time, he becomes conscious of his own monstrous wickedness, and he feels how his heart is pierced by the sharp tooth of remorse. But why is he wickeder than other men? Why was he born thus? Who made him what he is? An ardent longing seizes him to unravel this mystery. He hastens to his mother, and with drawn sword he adjures her to unveil to him the secret of his birth. Learning this, he becomes frantic with terror, shame, and grief. But his sturdy nature is not weakened; he does not yield to despair; instead, the hope of a laborious redemption, of a marvelous victory, urges and spurs on his proud spirit. He will learn to conquer Hell, to subdue himself, to thwart the designs of that accursed fiend who created him to serve his own ends, who has made of him a docile instrument of destruction and of sin. And he makes no delay. He goes to Rome, casts himself at the feet of the pope, makes confession to a holy hermit, submits himself to the harshest kind of penance, and swears that henceforth he will taste no food that he has not first wrested from the jaws of a dog. On two separate occasions, when Rome was besieged by the Saracens, he fights incognito for the Emperor and gains the victory for the Christians. Recognized at last, he refuses all rewards and honors, the imperial crown, even the monarch's own daughter, goes away to dwell with his hermit in the wilderness, and dies a saint, blessed by both God and men. In other accounts, he finally weds the beautiful princess who is deeply in love with him.