Poland is a country of rich history and many castles. Over hundred castles -fortesses were built by Teutonic Knights mainly in Northeastern part of Poland (regions: Masuria and Warmia called also East and West Prussia).
Teutonic Knights were invited to Poland in 1226 by Polish prince, Konrad Mazowiecki (Conrad of Mazovia). Their initial mission was to convert pagan Baltic tribes, especially Prussian into Christianity. As the history showed, inviting Teutonic knights was not a smart decision since they not only eradicate the pagan tribes but also were invading and destroying Poland several times until their liquidation and secularization in XVI century. But Teutonic knights build also incredibly fortified and beautiful castles. Throughout 200 years of their occupation, they built over 70 castles-fortresses. The biggest and most famous is Malborg (Marienburg), the capital of Teutonic order.
One of the Teutonic castles that was built in Dzialdowo in 1309 was a key protection point against the neighboring Mazovia region. About 1360, Dzialdowo was in the hands of a fierce Teutonic knight, who became a loner after a death of his Spanish fiance. Everybody disliked him, except that he had a charming sister who had a good influence on him. In one of the battles, the Teutonic knight caught and imprisoned a Prussian military leader. The man was put into the dungeon, but he was allowed to play the violin. He played so beautifully that the knight's sister started to visit him just to listen to the music. They fell in love. They were planning to escape by help of the guard since it was the only way for them to be together. But somebody betrayed them, and they were caught. The knight was very angry. He did not speak to his sister for weeks, finally he announced that she had to be married to another knight.
During the wedding her Prussian lover was called back from the dungeon and ask to play joyful music. He denied and the angry knight ordered to kill him. The young lady was devastated since she witnesses the killing. She died soon from sadness. Her soul keep wandering in the castle, sometimes the rambling of the horse ready to ride is heard ("Klechdy domowe", Warszawa, 1970, p. 254).
I recommend a book written by F. C. Anstruther, J. Sekalski, F. C. Anstrother (Editor), entitled: Old Polish Legends
Check Polish Tales - bilingual edition - written by famous Polish writer - Ignacy Krasicki: Polish Fables: Bilingual