Upon his return to Basel, Aeneas sided actively with the council in its conflict with the Pope, and, although still a layman, eventually obtained a share in the direction of its affairs. He refused the offer of the diaconate, as he shrank from the ecclesiastical state because of the obligation of continence which it imposed. Even the inducement to become one of the electors of a successor to Eugene IV could not overcome this reluctance. He supported the creation of the Antipope Felix V (Amadeus, Duke of Savoy) and participated in his coronation. Aeneas then was sent to Strasbourg where he fathered a child with a Breton woman called Elizabeth. The baby died 14 months later. Piccolomini served briefly as secretary to Felix, and in 1442 was sent as envoy to the Diet of Frankfort. From there he went to the court of Holy Roman Emperor Frederick III in Vienna, who named him imperial poet, and offered him a position at court, where he obtained the patronage of the emperor's chancellor, Kaspar Schlick. Some identify the love adventure at Siena that Aeneas related in his romance "The Tale of the Two Lovers" with an escapade of the chancellor. Aeneas' character had hitherto been that of an easy and democratic-minded man of the world with no pretense to strictness in morals or consistency in politics. He now began to be more regular in the former respect, and in the latter adopted a decided line by making his peace between the Empire and Rome. Being sent on a mission to Rome in 1445, with the ostensible object of inducing Pope Eugene to convoke a new council, he was absolved from ecclesiastical censures and returned to Germany under an engagement to assist the Pope. This he did most effectually by the diplomatic dexterity with which he smoothed away differences between the papal court of Rome and the German imperial electors. He played a leading role in concluding a compromise in 1447 by which the dying Pope Eugene accepted the reconciliation tendered by the German princes. As a result, the council and the antipope were left without support. He had already taken orders, and one of the first acts of Pope Eugene's successor, Pope Nicholas V (1447–1455), was to make him Bishop of Trieste. He later served as Bishop of Siena. In 1450 Aeneas was sent as ambassador by the Emperor Frederick III to negotiate his marriage with Princess Eleonore of Portugal.