Theodore of Octodurum

Saint Theodore of Octodurum (also "of Sion", "of Grammont"; German "Theodor von Sitten", locally "Joder"; also known as Theodulus, French "Théodule", Latin "Theodolus Sedunensis" etc.; 4th century) is the first known bishop of Octodurum, Alpes Poeninae province (present-day Martigny, Valais, Switzerland). 
He is the patron saint of Valais and of the Walser. His feast day is 16 or 26 August.
He is known to have participated in the Council of Aquileia in 381, his presence being preserved on the attendance list as "Theodorus Episcopus Octodorensis." 
He was also one of the signatories of a letter addressed by the Synod of Milan to Pope Siricius early in 390, informing him of their condemnation of the monk Jovinian and his followers.
He is said to have discovered the tomb of Saint Maurice, at which place he established the Abbey of St. Maurice, Agaunum.
Aloys Lütolf placed the beginning of his episcopate in the 340s, which would amount to a reign of more than forty years. At first he would not have had a fixed seat and in some sources is known as "bishop of the Helvetians".
It is possible that three distinct historical bishops with the name "Theodulus" or "Theodorus" are venerated as a single saint. 
The relics of Theodore, transferred to Sion probably in the 6th century, were lost during the French occupation of 1798. There are also accounts of his relics being moved to Bischofszell and by Ulrich of Augsburg to Ottobeuren.
His attribute is a devil bearing a bell. This represents a legend that the pope gifted a church bell to the saint, who forced the devil to carry the bell across Theodul Pass (formerly "Matterjoch", the naming of the pass after the saint is a 17th-century tradition). According to legend, metal particles from this original bell of Sitten were used in the casting of later bells.
Theodulhorn and Theodul Glacier are in turn named for Theodul Pass.