Black Guard should only be for faction leaders, they don't dish them out willy-nilly. On the table-top, I believe you can only have one per army unless you have the witch-king as your army's general. Right?
And unless your faction-leader is disloyal to his own throne that he sits upon, it should only increase personal security.

Also, I'd like to say that I personally believe there are far too many ancillaries and items for each faction, maybe you should only include the main ones.