The second missionary bishop of Livonia (1196-1198), Bertold was abbot of the Cistercian monastery of Loccum in Saxony before going to Livonia to commit himself to missionary work during the later years of Bishop Meinhard.
After Meinhard’s death, Bertold was appointed as new bishop of Livonia by Hartwig II, archbishopric of Hamburg- Bremen, and he returned to Livonia during the spring or summer of 1197. At the epsicopal centers of Üxküll (mod. Iķškile, Latvia) and Holme (mod. Martinsala, Latvia), Bertold met with fierce opposition from the local pagans, who threatened to kill him and rid themselves of Christianity. Consequently Bertold fled back to Germany, appealing for help to the pope, his archbishop, and the people of Saxony. Pope Celestine III willingly issued a crusading bull promising indulgence to those who would take up the cross and follow Bertold back to Livonia to fight the opposition and protect the remaining Christians.
In the spring of 1198 Bertold again returned to Livonia, having gathered a substantial army of crusaders in Lübeck from Saxony, Westphalia, and Friesland. On their arrival in Livonia, a truce was agreed on between the crusaders and the Livs, and a peaceful acceptance of Christianity was negotiated. This truce, however, was violated by the Livs when they killed several crusaders who were foraging in the countryside. In the ensuing battle the crusaders were victorious, but Bishop Bertold was killed when he apparently placed himself in the forefront of the attacking crusader army. According to the chronicler Henry of Livonia, Bertold thus became the first martyr of the young Livonian church. He was initially buried at Üxküll, but some years later his body was transferred to the cathedral church of Riga, where he seems to have been locally venerated for his alleged saintly virtues.