Soon, twelve prominent men of the area were soon brought to the Christian faith and baptized in a spring near the mountain Ostrabo. Their influence began a steady stream of pilgrims, who flocked to hear the Word of God and gaze upon Sigfrid's silken vestments, gold and silver vessels, and other beautiful objects brought with him from England. In 1008, Sigfrid baptized King Olof Skötkonung in a spring near the village of Husaby. Olof Skötkonung became the first Christian King of Sweden, which marked the beginning of the Christianization of Sweden. Sigfrid next traveled north to re-establish the See of Upsala that had been founded by St. [[Ansgar]], but the reversion to paganism was too strong in the region and he left in failure.
In 1014, the now-Christian King Olof Skötkonung assisted Sigfrid in the establishment of the Diocese of Skara in the Christian county of Västergötland, which became a suffragan of the Archdiocese of Hamburg-Bremen. The first diocesan bishop, Thurgaut the German, was consecrated by Sigrid
. Entrusting the administration of Växjö to Unaman and his brothers, Sigfrid left to spread Christianity in Denmark. At this time, Östergötland (East Gothland) also comprised the territory of the dioceses, and Sigfrid is said to have consecrated a [[vicar bishop]] in the Östergötland city of Linköping . While he was gone, however, a local greedy nobleman Gunnar Gröpe gathered a group of pagans together to kill Sigfrid's brothers and ransack the church in Växjö.
When Sigfrid returned from his mission, he found his nephews' heads in a weighed tub that was at the bottom of Lake Helgasjön. The bodies were buried deep inside a forest. According to Sigfrid, the heads still possessed the ability to speak and told him the names of their murderers. Sigfrid glorified God that He allowed Unaman, Sunaman, and Winaman to become martyrs. Soon Olof Skötkonung heard of the occurrence in Växjö and offered to execute the perpetrators, which Sigfrid refused. The King also offered to extract from them weregild, which the saint also refused. This made even the laying of foundation extremely difficult for the destitute bishop, but he eventually rebuilt the church and placed inside of it the relics of his holy kin.
He continued to preach and build churches into his old age, when he fell reposed in the Lord in 1045. His [[relics]] were place below the high [[altar]] of the Växjö church and performed many miracles until the shrine was dismantled after the Swedish [[Reformation]].