Secret society of the medieval Holy Roman Empire, what is now mostly Germany. The Order of the Holy Vehm was a society which practiced vigilante justice in an attempt to bring some sort of order to the petty statelets and princedoms of the totally disorganized Holy Roman Empire.
The Holy Vehm met as a court which convened in the dead of night. The possible wrong-doer who was to be judged by them was awakened by the servants of the Vehm, blindfolded and dragged to the secret location of the court. The blindfold was never removed and the person to be judged was never allowed to even look upon his accusers. If the accused was found guilty, the penalty typically involved their immediate death. None were immune from the justice the Vehm practiced, from the highest nobility to the lowest merchant or burgher. As far as I know, nobody considered peasants human enough to bother with anything as elaborate as a trial.
The Holy Vehm supposedly disapeared by the end of the 16th century, but many conspiracy theorists connect them with the Rosicrucians, the Bavarian Illuminati, and not to miss any bases, the Masons. Any good conspiracy theory has Masons in it. Much is made by some of the fact that their symbol was the same as that of the International Committees of the Red Cross (once chaired by Elizabeth Dole), but that's probably a coincidence, right?
This node inspired by somebody cooling Webby's writeup of vehmic.