Destroyer - B

Black Crusade = A Black Crusade is a specialized Crusade called by members of the Order of Destroyers and composed almost entirely of no other kind of Adept. A Black Crusade is called only in the most extreme of circumstances, always involving a world-ending scenario.
Black Crusades involve the forces of hell entering our world en masse, usually through means of a Hellgate or Greater Occult Summoning or some such evil. When an entire region has been taken over and all innocents are dead, or a spreading sickness that threatens all life on earth is on the loose. When a powerful evil is rising and it just has to die, then a Black Crusade is called against it.
When a Black Crusade is called, it is carried out with the most extreme prejudice. One Destroyer who had participated in a Black Crusade remarked that standing orders are simple: if it moves, kill it. 
Black Crusades destroy everything in their path, and thus little evidence is left afterward. Except for a lack of evidence, if that makes sense, since villages and towns in the path of a Black Crusade tend to go missing afterwards. Because of this, sometimes the hardest part of a Black Crusade isn't operating one, it's covering it up afterwards.  
Black Knights Chapter = A mercenary Chapter associated with the Destroyers, for more info see Black Knights.