He was married to Oda, daughter of Otto I, Margrave of Meissen-Orlamünde, whose lands he inherited, including the castle of Wanderslebener Gleichen.
Whether Egbert had participated in the Saxon rebellion remains unclear based on extant sources, but since he had nonetheless proved himself an opponent of the king, he was deprived of Meissen, which was given to Vratislaus.
Some sources report that after the death of anti-king Herman of Salm, bishops Hartwig of Magdeburg and Burchard of Halberstadt persuaded Egbert to turn against the king and himself aim for the crown.
In 1088, Egbert was besieged in his castle of Gleichen for four months by Henry, but on Christmas Eve he managed to escape, during the confusion of battle, with a relief army.
His remaining possessions fell to his sister Gertrude and her husband Henry the Fat, Margrave of Frisia, whose daughter Richenza married Lothair of Supplinburg, the later Duke and Emperor.