One of the optional side activities in Siege of Paris is hunting down Frankish Nobles. This guide on Where To Find All Frankish Nobles In Siege Of Paris For AC Valhalla will tell you the location of each of the Frankish Nobles so you can hunt them down, take them out, and finish the activity.
The Frankish Nobles are one of three new activities introduced with the Siege of Paris DLC. Alongside Rebel Missions and Roman Excavations, Frankish Nobles are special objectives hidden on the map that hide nobles that have been pushed away from their lineage due to the Nordic presence in Francia. Follow this guide to hunt them down and take them out.