Passion slaves, black silk girls, were an even rarer commodity on Gor, for one thing no Urthen girl could ever be a black silk pleasure slave. Black silk slaves were specifically bred for certain attributes, thick lips, luscious curves, and most had a club foot, for the intensive breeding to seek those attributes. Some passion slaves were kept in the slave pens in special rooms and never in their lives saw a male, until the time of her sale. At times black silk slaves are either the property of an Assassin (wearing his caste color), or exquisitely trained in seduction and dance techniques. However, in some areas black silks may denote an unowned slave.