Lourn was a Klingon male and one of the Clerics of Boreth. He held the title of Master.
In 2372, Worf often conversed with Lourn on their people when Worf was on leave after the destruction of the USS Enterprise. Lourn believed that their race would soon cause a conflict with another empire if none came to them. Lourn also chastened Worf for denying his Klingon nature by serving in Starfleet. After being cast out of Klingon society for opposing the invasion of the Cardassian Union, Worf went to see Lourn to tell him the teachings of Boreth were corrupting the Klingon race and could lead to its destruction. (DS9 novelization: The Way of the Warrior)
In 2373, Worf told Alexander Rozhenko that Lourn was wrong in his assertion that the violent Klingon nature could not be conquered, stating that the Klingon people could rise above their instincts if they wanted to. (DS9 - Day of Honor novel: Honor Bound)