legendary son of a duke of Normandy, born in answer to prayers addressed to the devil. He uses his immense strength only for crime. Directed by the pope to consult a certain holy hermit, he is delivered from his curse by maintaining absolute silence, feigning madness, taking his food from the mouth of a dog, and provoking ill-treatment from the common people without retaliating. He later serves as the Holy Roman emperor's court fool but, at the bidding of an angel, three times rides out disguised as an unknown knight to deliver Rome from Saracen attacks. His disguise is pierced by the emperor's daughter. He refuses her hand in marriage, however, and withdraws to a hermitage.

This is the legend as given in Robert le Diable, a late 12th-century romance; other versions are told in two 14th-century poems, and in the 19th century a distorted version of the legend supplied a libretto for Giacomo Meyerbeer's opera Robert le Diable.