The Witch Investigator who works for the Coven. They too come from one of the families on the Coven. There is no voting for the Inquisitor, the job is usually passed from mother to daughter.
The Inquisitor family in Ravencrest is the DeWitts.
The current Inquisitor of Ravencrest---Grace DeWitt---died in Season of the Witch, her daughter Scarlet is next to take over the position.