|By Lucas Cranach the Elder
via Wikimedia Commons
Then, the all of the big three royal marriage disasters happened to them: 1) They had no children. 2) They had no money--well, not enough at least. 3) They disagreed about religion. In an era when the division between Protestants and Catholics was still just heating up, religion was the hottest issue in Europe. Although both Eric and Sidonie had chosen to be Protestants, Eric changed his mind. He came to view his wife as a heretic. Some reports even alleged that he wanted to poison her; better a dead wife than a Lutheran one.
When Sidonie threatened to harm Eric's mistress, who was living in the castle with him, things got worse. Sidonie was a virtual captive. Neither her family nor the Holy Roman Emperor were able to alleviate her restrictions. Then Eric fell ill. Whom should he blame but his now detested wife? He accused her of using witchcraft against him or at the very least of poisoning him. Four women were tortured into confessions, which implicated Sidonie. The four were executed, while the intervention of the Saxons and the Emperor finally resulted in her acquittal as well as an income settlement for her.
Sidonie returned to Saxony and her younger brother, who was by then the duke, granted her the income from a Poor Clares monastery. She died there at the age of 56. The couple had never divorced, but Eric did remarry very shortly after her death. This marriage was also childless, but they were both Catholic and they seem to have refrained from accusations of poisoning each other.
More about Sidonie
Honour, a Poor Woman's Treasure on The History of Royal Women