Sorcerers of Tund

This group is pretty mysterious, but I've found some seemingly contradictory information, and am seeking perhaps clarification by someone more knowledgeable about them than me. The Knights of the Old Republic Campaign Guide for the Star Wars Saga Edition RPG states under Sith Mage:

"Though their heyday has come and gone, the last bulwark of Sith mages remains among the Sorcerers of Tund. They are conjurers of mind-pulverizing illusions and perpetrators of hellish transmogrifications, capable of incredible thaumaturgy. Though they rarely travel offworld, the sorcerers' intense investigations into the Force sometimes drive their own members mad."

However, that book has a few web supplements on the Wizards of the Coast website, the fifth one being about a Sorcerer of Tund, Karnak Tetsu. It states:

"Even though the original Sith were steeped in sortilege, sentient sacrifices, and wars, they lived spiritually serene lives, never doubting conflict's integral role to existence. Only with their introduction to methodic Rakatan malice did these Sith truly embrace the dark side. However, Sith priests interpreted the death of their Sith'ari in the Rakatan conflict as a sign to reject this concept. These heretics were banished from the Sith homeworld, following their instincts to the Force-soaked world Tund.

"This pureblooded Sith society combines science, ontology, and magic. Convinced by their Rakatan interactions that all sentients are Force-sensitive, the Sorcerers of Tund proclaim that the omnipresence of the Force (or "the Unity") illuminates the deception of dualities and multiplicity. Their cosmology views life as perfectly harmonious and the existence of true opposites as an illusion.

"The sorcerers have interactions with early Jedi, who view them as merely another Force sect, like the Jal Shey or Zeison Sha. However, following the Restoration -- and Karnak Tetsu's reign of terror -- Jedi label the sorcerers' hermetica as unqualified heresy. Unsurprisingly, the sorcerers are reticent in accepting outlanders, believing that only true Sith can grasp their truth. On one occasion, however, they welcome the few remaining Massassi and Kissai, descended from outcasts much like themselves."

http://wizards.com/default.asp?x=starwars/article/KOTORweben5

So on one hand, the information on the Sorcerers of Tund presented in the book suggests that they have fallen to the dark side, whereas their origin as described in the book's web supplement as given as them being exiled for having not turned to the dark side. Am I missing something? Is there perhaps a book or sourcebook or some other piece of canon that describes their fall to the dark side? There's a mention of Karnak Tetsu's "reign of terror" sometime after the Great Sith war. Is this elaborated upon elsewhere?

In addition, I'm curious if a date has ever been given for the group's destruction at the hands of Rokur Gepta.

 

I always interpreted it as: They left because they did not fall to the Dark Side, but later on they too fell to the Dark Side for whatever reasons.