The castle is first mentioned in 1219 as in arce Clanx, named after the Sax family holding in the Calanca valley. It was built by the Abbot of St. Gall Ulrich von Sax (1204–20) and his brother, the Abbey-Vogt Heinrich. The castle quickly became the center of the Abbey's lands in Appenzell. In 1236 Heinrich's uncle, the famous knight and minnesänger Heinrich III von Sax, took over the castle. During a contested election for Abbot of St. Gall in 1272, Ulrich von Güttingen received support from the Habsburgs in exchange for a promise to take the castle and lands away from the Sax family. Two years later, in 1274, Heinrich III was forced out and the Habsburg knight Ulrich von Ramschwag was given the castle. In 1277 Abbot Rumo von Ramstein traded Blatten Castle and other estates with Ulrich von Ramschwag, bringing Clanx back under the Abbey's control. In 1278 the Appenzellers revolted against the Abbot and unsuccessfully attacked Clanx. In 1289, the Habsburgs attacked Clanx in an attempt to gain control over Appenzell. After a six-week siege, the Habsburg forces paid the castle's defenders a bribe to open the castle gates. The defenders departed in peace and the castle was burned.
