[1] He was a significant diplomat and go-between in the affairs of his times, and was nicknamed the "cardinal with three hats", which he obtained successively from Urban VI, Clement VII, and Boniface IX.

He was a Canon of the cathedral of Padua in 1350 at the age of twenty,[4] and held the dignity of Archpriest from 1356,[5] though he was only in minor orders, when he was appointed bishop of Treviso by Pope Clement VI on 1 June 1358.

[15] In 1372, Pope Gregory XI summoned Pileo to Avignon, and sent the archbishop along with the Bishop of Carpentras, Guillaume l'Estrange,[16] as his nuncios to King Charles V of France.

Pope Gregory wrote a letter to the King of France, threatening ecclesiastical censures against those who should reject the proposals of the nuncios.

[17] In 1376, Archbishop Pileo was drawn into the expansionist military adventures of Barnabò Visconti of Milan, who threatened Tuscany as well as territories belonging to the papacy, including Bologna and the Patrimony of S. Peter.

[18] In 1377, an opportunity arose which might have allowed Pope Gregory to repay Archbishop Pileo for his expenses in the papal diplomatic service, and to compensate him for his losses in Ravenna.

[21] Urban VI had sent him as a legate to Germany and Hungary, a journey made all the more critical since the Emperor Charles IV had died on 29 November 1378, and his successor Wenceslaus had sent representatives to Rome.

He is accused of having used his legatine powers to the maximum while he was in England, lifting excommunications and cancelling vows of pilgrimage, receiving generous gifts for his services.

The pope's real purpose was to enhance his own family's fortune, in particular those of his nephew, Francesco Butillo, who had been cheated by Charles of Durazzo out of his share of the spoils of the destruction of the expedition of Louis of Anjou.

[36] Pileo fled to Genoa, where he and Cardinal Galeazzo Tarlati da Petramala repudiated Urban[37] and sought refuge in Avignon.

[41] Having become exasperated at the negotiations of the Florentines, to whom he had suggested a general council to resolve the schism, Pope Clement VII assembled an army, mostly of Gascons and Bretons, and, on 4 May 1388, appointed Cardinal Pileo as his legate for Tuscany and Lombardy.

Pileo and the army, joined by the forces of Rinaldo Orsini, then moved against Orvieto, which they seized and in which they installed a friendly government.

[44] Cardinal Pileo was reinstated in the Roman Obedience by Pope Boniface IX in his previous post as Bishop of Tusculum, but not until 13 February 1391.

[46] Clement VII labelled him infamem transfugam, impostorem, ac fidei venalis hominem (a disreputable turncoat, an imposter, and a man with his loyalty for sale).

[47] In 1392, Pope Boniface appointed Cardinal Pileo his Legate in Umbria, the Romagna, and the Marches, with a salary of 3,000 zecchini.

He helped the pope by loosening the grip of the Malatesta family on Todi, and he calmed the strife between Guelfs and Ghibellines in Perugia, at least for a short time.

[citation needed] On Christmas Eve 1398, the Pope was ill, and Cardinal Pileo di Prata presided at the Vespers service in the larger chapel.

[50] In 1398, he was assigned to a commission of three cardinals to judge the crimes of Count Onorato Caetani of Fondi, who had been the protector of the adherents of Clement VII (Robert of Geneva) since April 1378.