a native of Gaul, was private secretary to Attila and his brother Bleda, to whom he was recommended by Aetius. Constantius was a very rapacious man. Having been sent to the court of Theodosius II. to negotiate a lasting peace, he promised to promote the interest of the emperor if he would give him a rich woman in marriage. Theodosius offered him the hand of a daughter of Saturninus, Comes Domesticorum, who was very rich, but who had been carried off by Zeno, Praefectus Orienti. Constantius having complained about it to Attila, this king threatened to invade Greece if the emperor did not produce the woman, and as Theodosius was unable to do so, Attila availed himself of the circumstance as a pretext for making war upon the emperor. During this war (A. D. 441) he laid siege to Sirmium.
The bishop of Sirmium sent a considerable quantity of gold and silver vessels belonging to his church to Constantius, requesting that he would keep them as his ransom in case the town should be taken and he fall into the hands of the victors. But Constantius kept those vessels for himself, and pledged them to a banker of the name of Sylvanus. When after the capture of Sirmium and the captivity of the bishop, Attila was informed of the robbery, he requested Theodosius to give up Sylvanus and his property, and Theodosius having refused to comply with the demand, Attila prolonged the war on that ground. Constantius was afterwards charged with high treason, and crucified by order of his master. (Priscus, in Excerpt. de Legyat.
pp. 54, 57, 69, ed. Paris.)