 "nevertheless, the minstrels and ballads filled this void with beautiful literary creations devoid of any historical reality".It was at this time that the "Leyenda de Cardeña" concerning El Cid (13th century) was born.According to this legend, Alfonso VI was forced by El Cid to take an oath to deny that he had been involved in his brother's death, thus giving rise to mutual distrust between them despite Alfonso VI's efforts at rapprochement by offering his kinswoman Jimena Díaz to El Cid in marriage as well as the immunity of his patrimony.