Meistras (culture)
The Meistras were the house servants for the Magi. Constantly being in the houses as servants put them in a unique position. They were able to move freely and mostly were left to their own devices by their masters. Their hubris and aura of superiority made them not look twice at the slaves and their daily chores. It was this non-caring attitude that allowed the Meistras to be the first of the slave castes to begin to have Magi blood running through their veins and the first to start learning the words of power. They were allowed to start families and could pass off a child as their husbands when in reality it was not.
Cenwares invasion allowed the Meistras to seize the initiative and attack from the inside, slaughtering men, women and children before they fully could comprehend what was going on. Before Cenware, revolt had been all but a pipedream, but now freedom was a very real proposition.