Wait, they were kind of like SPECTRE or the League of Assassins? That's awesome! I only came across them in 3e and thought the public facing Nazis was a bit dumb (my opinion only). Shadowy groups that use intermediaries are much more fun.
The Scarlet Brotherhood, in the original, was a shadowy organization about which almost nothing was known except that it had a tripartite caste structure (with thieves at the bottom, assassins in the middle, and monks at the top), that it had a walled fortress somewhere on the remote plateau, and that it had spies and agents embedded in the other nations.
Oh, and that it was evil and claimed superiority for the Suloise race.
It is said that an order of monastic religious militarists was founded long ago on the remote plateau south of the closed city of Kro Terlep. This order is purported to espouse the cause of the Suloise as the rightful rulers of all the Flanaess, claiming superiority of that
race above all others, and embracing evil as the only hope of achieving its ends. Supposedly the Scarlet Brotherhood is the fruition of these aims, and it now controls the whole of the land from the Vast Swamp to the tip of the peninsula. Brothers of the Scarlet Sign are reportedly hiding as trusted advisors or henchmen in many courts and castles in the north, spying for their master and ready to strike.
The Brotherhood is tripartite according to tales told, with thieves at its lower ring, assassins next, and then the smallest and highest ring of monks as superior. The leader of the thieves is called "Elder Cousin," that of the assassins is known as "Foster Uncle" - thus other thieves are entitled "cousins" and assassins "nephews.''
The temple and monastery of the Scarlet Brotherhood is supposedly a fortress and walled town unto itself, guarded by soldiers. humanoid legions which are being readied for future conquest and monsters trained to serve the Brotherhood.
-The Scarlet Brotherhood by Gygax, Greyhawk Campaign Setting at 33.
One theme I have had running through Greyhawk Campaigns is a twist on the Gygaxian humanocentric idea. In my Greyhawk, there is a lot of strife between humans and other races (or between some races, such as the traditional dwarf/elf divide, or drow/elf divide) - the reason for this isn't any kind of "natural inclination," but because of long-ago efforts by the Suloise, continued now in secret by the Scarlet Brotherhood, to flame and stoke divisions for their own end. Even now in my Greyhawk, you have agents of the Scarlet Sign amongst the Drow, the Duregar, and so many others continuing to subtly (and not so subtly if need be) alienate them from others.
Or, to put it another way, "Where there's smoke, there's racist Nazi monks flaming the fires."
(That said, I think that particular subject matter would be a little much for a general WoTC offering ...)
