Passauer Vertrag
In 1549–50 and again in 1555 he took part in the papal elections at Rome. The situation of the bishopric worsened in 1552, when it was devastated by the troops of the former ally Maurice, meanwhile Saxon Elector. The emperor's younger brother King Ferdinand I, now in charge and prepared to compromise, concluded the Peace of Passau with Maurice, which led to the 1555 Peace of Augsburg with the Lutheran princes. Otto's advice was no longer in demand and with the abdication of Charles V the next year, his powerful position finally was lost. He once more went to Rome in 1559 and was there made the head of the Inquisition and, in 1562, Cardinal-Bishop of Albano. In 1567 he held a diocesan synod at Dillingen.