The Qowat Milat were an order of Romulan warrior nuns. They were an all-female group; while a male could train in their ways, he could never truly be one of them. The Qowat Milat were the most feared enemies of the Tal Shiar.
The primary teaching of the Qowat Milat was the Way of Absolute Candor, i.e. the total communication of emotion without filter between thought and word; this ran counter to everything that mainstream Romulans held dear. According to Zani, theirs was a "house of truth". Another of their sayings was "a promise is a prison." (PIC: "Absolute Candor")