Dark Sun: TDH
The Veiled Alliance
A secret society of preservers, dedicated to the downfall of defiling magic and those who wield it. Since this includes the sorcerer-kings, the Alliance is effectively a rebel movement; the sorcerer-kings seek to suppress them and their activities are illegal almost everywhere.
Because of this the Alliance operates with extreme secrecy and caution. It is organized into independent cells and takes orders from no central authority.
The Veiled Alliance will help anyone using preserving magic, although simply being a preserver does not guarantee membership. All Veiled Alliance members swear solemn oaths never to use defiling magic. Violators are hunted down with extreme prejudice.