Moved by the cause of the Count of Anjou and Maine, he played a significant role in the battle between his liege lords and William the Conqueror.
Despite a four-year siege (1083–1086), the city of Sainte-Suzanne, defended by Hubert II, was the only castle that William the Conqueror never succeeded in taking.
The Beaumont family, later Beaumont-Brienne, dominated this part of Maine from the tenth to the thirteenth centuries.
[3] She appears with her husband in several historical accounts, notably at the confirmation of the chapel of Saint-Aubin du Lude, around 1090, and at the donation of Saint-Flaceau to the abbey of Saint-Vincent.
With her daughter Godeheult, the future abbess of the abbey at Étival, located in Chemiré-en-Charnie, Ermengarde frequently visited various convents.