The Robber Knights
The priests of Nilith realized the need for a knightly order, both as a martial force and also to entice the sons of noble families to the faith. Unfortunately, the lack of seasoned leadership left most of the direction to those young knights, which has led to a very unorthodox organization. At heart, the charge of the knights is to seek out undead forces and either bend them to the will of Nilith, or destroy them. If the church of Nilith has need of military force, the knights are to step in as leaders of the undead legions. Between these duties, the knights jockey for rank amongst themselves with displays of wealth, their armor adorned with the spoils of their wars and crusades.
Philosophy
To put it bluntly, the knights believe in growing strong and leaving a pretty corpse. Ultimately, the goal is to become impressive enough that the Goddess blesses them in joining her undead legion as a death knight or vampire knight. They believe her favor can be gained by adding powerful undead to her legions, or by eliminating undead that refuse to bend the knee, those that are declared heretical to the Nilithim.
Organization
At present, the only leadership is an ancient vampire knight, Anguiris Sarcrosta. He claimed the title of Grand Marshal with the blessing of the Nilithim, and as such none of the lesser, mortal knights have challenged him… yet. However, he has instilled such an outlook on the rest of the order, and it is not uncommon for promotions to result from challenges by combat. Ranks are gained on the deaths of those above. In this way, only the strong survive, and the weak are added to the ranks of undead troops.
While most of the knights agree that might makes right, there is a special level of status awarded to those who have amassed wealth. This usually takes the form of elaborate armor and weaponry, with tokens and prizes adorning it from their many conquests. Because of this, there is no uniform to the Robber Knights, aside from a fondness of a bone or skeletal motif. While some of the knights incorporate the holy symbol of Nilith into their armor, most believe that the gaudy nature of their gear is enough.