In 1121, under the patronage of Lothair who was not yet Emperor, Vicelin began his work among the Wagrians, and in 1149 he became their Bishop with his see at Oldenburg. He died in 1154. It was under the auspices of Henry the Lion, now Duke of Saxony, that Berno preached to the Obotrites, converting the Wendish Prince and becoming Bishop of Mecklenburg.