Eric XIV (13 December 1533 - 26 February 1577) was King of Sweden from 1560 until he was deposed in 1568. Eric XIV was the son of Gustav I of Sweden and Catherine of Saxe-Lauenburg. He was also ruler of Estonia, after its conquest by Sweden in 1561. He was intelligent and artistically skilled, as well as politically ambitious. However, early in his reign he showed signs of mental instability, a condition which eventually led to insanity. Wikipedia
The definitive Wikipedia entry for Eric Xiv Of Sweden. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Eric_XIV_of_Sweden
Mental derangement was a dominant feature of the Wasa family that ruled Sweden from 1523 until 1689. www.xs4all.nl/~kvenjb/madmonarchs/eric14/eric14_bio.htm