The first mention of Rengerswil Castle in the 13th century tells of a turbulent local history. In 1226 Diethelm, the Count of Toggenburg and lord of the castle of Rengerswil, is said to have lured his brother into the castle and murdered him. Diethelm thus triggers a war in which the castle is besieged and then falls. In the peace treaty of 1234 it was given to the abbot of the St. Gallen monastery, but shortly afterwards it was returned to the Counts of Toggenburg.
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It is not known whether the siege resulted in major damage to the castle – the Gyger map from the 17th century shows a building surrounded by moats near today’s Schlossberg.
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