Dev Vo'Qul (translation: "guide of fire") was a title held in the Klingon Empire by an agent of justice. Klingons appointed to this position were tasked with avenging wrongs done to the Empire.
On Stardate 7251.1, the Dev Vo'Qul was dispatched on a vessel to bring Starfleet Captain James T. Kirk to justice for his crimes against the Empire during the USS Enterprise's five-year mission. (TOS comic: "Year Five, Issue 13")