Prince Popiel (or Duke Popiel), legendary 9th century ruler of the Polanie or Goplanie tribe. For now there is no archeological evidence of the existence of any such person. According to legend, he was the last member of pre-Piast dynasty, Popielids. According to the chroniclers Gallus Anonymus, Jan Długosz and Marcin Kromer, as a consequence of bad rule he was removed from the throne and died eaten alive by mice (or rats) in a tower in the Kruszwica settlement.
As the legend goes, Prince Popiel was an inadequate ruler who cared only for wine, women, and song and who was greatly influenced by his wife Ryksa, a beautiful German princess who desired power. Because he was a poor ruler, his twelve uncles tried to remove him from the throne, but at his wife's instigation he had them poisoned at a banquet. Instead of burning the bodies as was the custom, he had them cast into Lake Gopło.
When the people of the tribe saw what Popiel and Ryksa had done, they turned against them, and the prince and princess took refuge in a tower near the lake. As the story goes, a multitude of mice and rats which had been feeding on the unburnt bodies of Popiel's uncles attacked the tower, chewed through the walls, and ate Popiel and Ryksa. A ruined tower that still stands at the lake is called "mouse tower" after this legend. (But the tower is not old enough to be the tower in the story.)