His son, Hugo, inherited the Bregenz lands around Lake Constance, including Sargans.

This Hugo, who adopted the name Montfort und Werdenberg built or expanded Sargans Castle before his death in 1228.

In the mid-13th century the Montfort und Werdenberg lands were divided between Hugo of Werdenberg-Heiligenberg and his brother Hartmann of Werdenberg-Sargans.

In the Battle of Näfels in 1388, the count commanded a wing of the Austrian army that was supposed to cross the Kerenzerberg Pass.

The cost of the war, as well as other expenses forced Johann I to sell the castle and village to Leopold of Austria.