[citation needed] He reigned from 1163 until 1214, when he surrendered his fiefs to Simon de Montfort, Earl of Leicester and leader of the Albigensian Crusade.
[4] In 1179, Roger II Trencavel, Raymond V of Toulouse, and Bernard Ato had all been excommunicated by Pons d'Arsac under the twenty-seventh canon of the Third Lateran Council for their lack of strong opposition to heresy.
[5] In that same year Bernard Ato did homage to Alfonso II of Aragon for his viscounties and made an alliance with Alfonso against Raymond V.[2] In June 1187, Bernard Ato granted all his lands within the Diocese of Agde (omnes dominationes vicecomitatus) to the diocese and was then accepted into the cathedral church as a canon.
Bernard Ato swore fealty to William VIII of Montpellier for part of his domains in 1189, January 1191, and finally 1195.
[citation needed] On 2 May 1214 Bernard Ato and his wife Guillelma signed over their viscounties to Simon de Montfort, 5th Earl of Leicester, the leader of the Albigensian Crusade.