Secundum Naturae Ordinem Wesen

The Secundum Naturae Ordinem Wesen (Lat. "Wesen (who live) according to the natural order"), also known as the Wesenrein, is an ancient organization founded during the middle ages to keep Wesen pure. Each member wears a mask called a gleichheit (Ger. "identity") and during tribunals they wear hooded robes with a wolfsangel on the front. Most members wear a black robe, but the "grand master" wears a red robe and the Purifier wears a white robe.

To them, inter-marriage is a crime against man and nature. They often use a wolfsangel in some form as a warning to Wesen in an inter-species marriage. Another type of warning they will carry out is to hang a dead animal outside the home or workplace of their targets as a "final notice" for the couple to split up. Eventually, they will kidnap their targets with the plan to kill them after a rigged trial.

Trivia

 * The group bears a certain resemblance to the Ku Klux Klan (at least historically), being a purist organization who burn symbols into the property of those who 'defy' them, and capable of extreme violence in defense of their beliefs.
 * They also share some similarities with various Neo-Nazi groups. A prime example being their flag, essentially a Nazi flag with a wolfsangel in place of the swastika.