Wizards

Wizards are a type of spell-caster, found throughout the Empire. Unlike Warlocks, who gain their knowledge of magic as pact of a 'pact' (contract or bargain) with some power (called a 'patron'), or Sorcerers who are born with their magic due to having an extraplanar being somewhere in their ancestry, Wizards learn to wield Arcane Magic as an intellectual exercise (most often under the tutelage of a school funded by the Chancery).

Power source

All Wizards are taught to manipulate Arcane Magic, a form of power is inherent with the Prime Material Plane due to its connection to all of the other Inner planes simultaneously. Wizards understand that literally anyone with enough patience, and some aptitude for complex calculations, can learn to tap into this power source and use it to create effects based on a series of equations that lay-people call "spells". Such mastery of the technique takes years though and most scholars of Arcane Magic rarely manage to grasp the nuances of the craft required to cast more than a few cantrips.

Chancery Outlook

The Chancery was formed with the purpose of identifying and containing magical threats to the Empire and soon realised that the best way to do this on a long-term basis was to actually take over and regulate the teaching of magic. As such the Chancery knows who is learning magic, their relative aptitude and their level of attainment. Additionally it is also a source of income for Imperial coffers as such training can be charged at a premium to the Empire's wealthy elite. Students who display "anti-establishment leanings" can be identified early and directed into less academically challenging work such as retail, accountancy or swift execution.

The Chancery then is not overly worried about Wizards trained from within the Empire. It has those threats well contained allowing it to focus on threats from outside the Empire's borders.