Complex sentence: The lords of Mirwart came into conflict with the monks of the powerful Saint-Hubert Abbey, supported by the Prince-Bishop of Liège who wanted to extend his power in this region to the disadvantage of the Dukes of Lorraine.
Split into simpler sentences: The Lords of Mirwart came into conflict with the monks of the powerful Abbey of Saint-Hubert. The latter were supported by the Prince-bishop of Liège who wanted to extend his power in this region to the disadvantage of the Dukes of Lorraine.