The Hermetic Order of the Golden Dawn
In the 19th century, there was a great surge of public interest in the occult. With no input or guidance from the Academy, many private citizens turned to whatever sources they could find, in pursuit of magical knowledge. Some, such as the members of the Hermetic Order of the Golden Dawn, found it.
Generally speaking, wielding "pure" magic as wizards do (that is, pure of any influence from outside entities), is a very difficult pursuit requiring many years of intense practice and meditation merely to grasp the fundamental concepts. Few are willing to wait so long, and in the 19th century--much as it was in centuries past--there are plenty of outsiders willing to empower those who seek their aid...for a price.
As the High Council would have it, practitioners of the Hermetic Order are warlocks, violators of the Laws of Magic, and enemies of wizardry and mankind. Unfortunately, they also tend to be populated by some of the most powerful and visible members of mundane society, and as such, are difficult targets for the Eldritch Knights, particularly in an era where technology allows mortals to rival the power of wizards.
Today, the Hermetic Order, and many other, smaller orders, practice arcane traditions, some of which are genuine invocations of outside power, while many others are nonsense planted on the racks of bookstore shelves by wizards; precious few in these orders have access to true power, but those who do enjoy free reign in human society, easily rising through its ranks with the help of their patrons...until the price is ultimately exacted upon them.