You can only hear a rumor if you don't have all of certain same level artifacts. They require to have reached 8, 14 or 20 points from events, then the artifact will be found. Rumors come in 3 flavors : minor, medium and major. You can authorize him to search for the artifact or select another councillor. If you're not Zunist, your councillor may hear a rumor of an artifact. Some Great works and their upgrades grant artifacts through event chains.Contribute to a Christian Crusade for a fraction of the Crusade War Chest.
See Selecting councilors for artifact-hunting abilities. For important yet destructible artifacts, it is recommended to grant a castle to avoid the 50% chance of artifact destruction.
Revoking a vassal down to baron tier will force them to use agnatic succession.
