Around 1100 Richenza married Lothair of Supplinburg, who upon the death of the last Billung duke Magnus was enfeoffed with the Duchy of Saxony by King Henry V of Germany in 1106. After Lothair was elected King of the Romans in 1125, she was crowned queen consort by Archbishop Frederick I of Cologne. She also took part in Lothair"s second Italian expedition in 1136-1137, whereby she presided over hearings of the Imperial court and issued several deeds.
This act brought both the Northeim and Brunonid lands into the hands of the House of Welf.
On Pentecost the following year, however, the Princes of the Holy Roman Empire convened in Bamberg to elect Conrad III King of the Romans. Conrad vested the Ascanian count Albert the Bear with Saxony and Henry died soon after, in the autumn of 1139.
Young Henry was finally appointed Duke in 1142. His mother Gertrude ruled as regent until his majority.
Her grave goods included a simple and elegant lead crown.