Tello was the Bishop of Chur

Bishop of Chur

The Bishop of Chur is the Ordinary of the Roman Catholic Diocese of Chur, Grisons, Switzerland .-History:...

 from 758/759 until his death. He was the last member of the ecclesiastical dynasty of the Victorids

Victorids

The Victorids were a powerful family in Rhaetia during the seventh and eighth centuries, dominating the region politically and controlling the diocese of Chur. The family is termed after the continued use of the name Victor....

 to wield power in Rhaetia through his control of the bishopric. His will is one of the earliest surviving records from Graubünden

Graubünden

Graubünden or Grisons is the largest and easternmost canton of Switzerland. The canton shares borders with the cantons of Ticino, Uri, Glarus and St. Gallen and international borders with Italy, Austria and Liechtenstein...

 and is an important source for the history of Rhaetia in the eighth century.

According to his will, dated 15 December 765, and the Liber de feodis of 1388, he was a son of Victor, the praeses

Praeses

Praeses , is a Latin word meaning "Seated in front of, i.e. at the head ", has both ancient and modern uses.-Roman imperial use:...

of Rhaetia, and his wife Teusenda. It is also mentioned in the will that he had brothers and sisters, though they are left unnamed. His episcopate can be demonstrated from 759 and he held, concurrently, the title of praeses, which had been his father's. He thus held both the spiritual and the temporal authority in the province.

He is mentioned in the Vita sancti Galli of Walafrid Strabo

Walafrid Strabo

Walafrid, alternatively spelt Walahfrid, surnamed Strabo , was a Frankish monk and theological writer.-Theological works:...

 under the year 759 or 760. In 762 he participated in the Council of Attigny on the Aisne

Aisne

Aisne is a department in the northern part of France named after the Aisne River.- History :Aisne is one of the original 83 departments created during the French Revolution on 4 March 1790. It was created from parts of the former provinces of Île-de-France, Picardie, and Champagne.Most of the old...

 as a suffragan of the Archdiocese of Mainz. His signature appears on the conciliar documents. Tello is elsewhere documented in the Verbrüderungsbuch

Verbrüderungsbuch

Verbrüderungsbuch is the German name for registers from monasteries in the Middle Ages. They contained lists with the names of sponsors and benefactors, as well as persons in close spiritual contact with a monastery, so that they were actively remembered in the prayers of the monks...

(fraternity book) of the Abbey of Reichenau. He began the construction of the cathedral, which has an unusual crypt and was renovated in the Romanesque style

Romanesque architecture

Romanesque architecture is an architectural style of Medieval Europe characterised by semi-circular arches. There is no consensus for the beginning date of the Romanesque architecture, with proposals ranging from the 6th to the 10th century. It developed in the 12th century into the Gothic style,...

.

His death date is secured as 24 September, but the year is unknown, probably the same year as that of his will, which was dated to December. He bequeathed his extensive landed and movable wealth, which was concentrated in the lower Surselva between Flims

Flims

Flims is a municipality in the district of Imboden in the Swiss canton of Graubünden. The town of Flims is dominated by the Flimserstein which you can see from almost anywhere in the area....

 and Trun

Trun, Switzerland

Trun is a municipality in the district of Surselva in the canton of Graubünden in Switzerland.-Geography:Trun has an area, , of . Of this area, 23.6% is used for agricultural purposes, while 34% is forested...

, to Disentis Abbey

Disentis Abbey

Disentis Abbey is a Benedictine monastery in the Canton of Graubünden in eastern Switzerland, around which the present town of Disentis grew up.-Foundation to 19th century:...

, with which he had had close ties.