Well, I don't know much about it either. They are usually the ruling class that is with a title T'zar or Tsezar, which is also the bloodline of Ceaser (Tsezar, as it was pronounced originally). Kaiser has also the same origin.

I know they were primarily involved in the Templar attacks to retake Jerusalem. This topic needs a lot more review but you can see how hidden it still remains. Hope you find more on the topic!