Lower Satakunta. The duchy thus formed was given extraordinarily independent feudal rights by the King. Additionally, John was appointed Governor-General of Finland, including all the other areas beyond the Gulf of Bothnia and up to the eastern border. Those areas were however not held by feudal right but with John as a royal appointee. Duke John settled in Turku, where he created a cultivated princely court at the Turku Castle. He was an enthusiastic patron of arts and architecture and decorated the castle with splendor never before seen in Finland. Before his marriage, he had a Finnish mistress, Kaarina Hannuntytär. Several Finnish and Swedish families claim descent from their offspring. After the death of his father, John ran his own foreign policy which at times was at odds with his elder brother King Eric XIV of Sweden (reigned 1560–1568). In domestic affairs too, John soon opposed the King, together with a party of high nobility who all were against an increasing centralization of the government. On October 4, 1562, against the wishes of the King, John married his first wife Princess Catherine Jagellonica (1526–1583), daughter of King Sigmund I of Poland (1467–1548). Eric regarded this conduct as rebellion. John and Catherine were imprisoned at Gripsholm Castle the year after their wedding and after a siege of Turku Castle and its conquest by royal troops. The imprisoned Duke considered himself to have kept his title, while the duchy itself was administered by royal officials. Eric was deposed by John, who had been released, acting with leaders of the nobility in 1568, and John and ascended the throne of Sweden, reigning until his death in 1592 as King John III. In 1589 he appears to have made arrangements to grant the Duchy of Finland at birth to his younger son Duke John (see below). In 1581, King John III additionally assumed the subsidiary title of Grand Prince of Finland and Karelia. Karelia was soon dropped from the title and considered part of Finland in an expanded eastern extent. The title became established in Latin renderings, and later in the 19th century also in English, as Grand Duke of Finland, however using the Finnish (ruhtinas) and Swedish (furst), for a crowned or sovereign prince, in its local renderings. John the Younger Shortly before his death, King John III, the previous Duke of Finland, gave his old Duchy and its title as a royal