The Oath Rod of Kurgi
This black staff is carved out of ancient wood and inscribed with the Oath of Kurgi, Slave to Unreason. Hidden among the other runes on the staff are skulls that endlessly shout out their mad anguish and blather oaths to Unreason. Those struck by the rod will lose their minds. The wielder can point the staff at living beings to mark them as Kurgi's to take.