The Tahjai.

Once they belonged to the Order of Magic users of Vaim, before they split themselves off seeking more power and control as well as more freedom.
The leaders of the Tahjai, several powerful archmagii decided that if they were to win this war for dominance from their rivals the The Faithful they needed to kill off any allegiance to its teachings.
So they declared them traitors and claimed the children gifted with magic as quickly as they could.
The younger the better…That way they could stamp out any opposition.
There were those that the Tahjai formed, but that did not necessarily mean they became part of the Tahjai themselves. The order was rather particular in accepting new blood.
They could be divided into several groups.
The Enforcers, these were those on the ground doing the menial tasks of maintaining order and checking new potential magic users.
Then there were the Educators, they could be leaders of covens or schools, instructors within the wealthier families.
There were the Imperii, the judges and magical priests, they performed rituals or judged criminal cases involving magic. 
The Battlemages were different set, though often found crude by their fellow Tahjai, they were the ones who were given command over others and free reign, allowing them to pass judgement as they saw fit, regardless whether the Imperii agreed upon it.
And then there were the Scolare, the eternal students, scholars and scientists who were not afraid to get their hands dirty in order to satiate their own hunger for knowledge.
Their stronghold is known as Waelwold, a place of terrible rumours, a place where even death itself would have trouble finding you. By the time it had, you had already longed for its embrace over and over again.
All those that were born with magic would serve the Empire, if not as a Tahjai then as a simple servant or even slave to a master.