Found this folk-tale while researching castles for the boardgame:
Hatto II was a cruel ruler who oppressed and exploited the peasants in his domain. He used the tower as a platform for crossbowmen and demanded tribute from passing ships, shooting their crews if they did not comply. During a famine in 974 the poor people were without food, and Hatto, having all the grain stored up in his barns, used his monopoly to sell it at such a high price that most could not afford any.
The peasants were getting angry and organizing to rebel, so Hatto devised a cruel trick. He promised to feed the hungry people and told them to go to an empty barn and wait for him to come with food. The peasants were overjoyed and praised Hatto heartily, and all of them journeyed to the barn to await his coming. When he showed up with his servants, he ordered the barn's doors shut and locked, then set the barn on fire and burned the peasants to death, derisively commenting on their death cries with the words "Hear the mice squeak!"
When Hatto retired to his castle, he was instantly besieged by an army of mice. He fled the swarm and took a boat across the river to his tower, hoping that the mice could not swim. The mice followed him and rushed into the river by the thousands. Many of them drowned, but even more crawled onto the island. There, they ate through the tower's doors and crawled up to the top floor, where they found Hatto and ate him alive.
- source
