In a thread discussing the origins of the Sith Order led by Darth Krayt in Legacy, I suggested that the new order might have its roots in the True Sith Empire of the Unknown Regions from KOTOR2. My chief premise for this argument was that the True Sith would have the Sith teachings necessary for any order of Dark Siders looking to make themselves into proper Sith, and that they would be one of a handful of sources for such teachings- perhaps the only source available to a truly new Order. Sidious seems to have secreted away most of the Sith knowledge amassed by Bane's order, and what didn't die with him and Vader seems to have been scattered all over the place. Sure, Lumiya gets a hold of Adas's Holocron, which could in theory be enough. It wouldn't be definitely enough, though. And so I asserted that, except for the True Sith, there was no plausible store of Sith knowledge great enough to birth an Order powerful enough to rule the galaxy. I was apparently mistaken. From the very game I cited the True Sith from, no less. I was thinking about where one would go to absorb Dark Side energy, which led me to thinking about Atris's corruption by the Sith holocrons she was keeping. Then I stopped for a moment... and backed up a bit. As those who have played KOTOR2 will well recall, the end of the game pits the Exile against Atris in the meditation chamber of the Telos Academy, at one of Telos' poles. Said meditation chamber is filled with Sith holocrons, their angry red glow and malicious whispers swelling Atris's madness. The Exile defeats her nonetheless, and then leaves- personally, I chose to leave Atris to the Sith holocrons. Yet Telos IV is spared from Darth Nihilus's attack. The Telos Academy and its holocrons all survive, and apparently the Handmaiden takes over as the Academy's caretaker. Beyond that, there seems to be no mention of the Academy or its precious artifacts again in the EU. At the very least, Wookiepedia's entry ends inconclusively. There were at least a dozen Sith holocrons at the Telos Academy. Indeed, that's a conservative estimate. Were I being more liberal, I'd put it at around twenty, perhaps even twenty-four. And we have no idea what happens to the Academy after KOTOR2. So, there are as many as two dozen Sith holocrons unaccounted for. Even allowing for half that amount eventually being moved from Telos and snapped up by Kaan, Bane, Millenial, Sidious, etc., or locked away by the Jedi, or even kept in some wealthy collector's study as a paperweight, that would still leave us with ten full repositories of Sith teachings not in the hands of any of the major players of the GFFA. Yeah. You could probably start a pretty nice Sith Order with all that.
Trayus, these are more than likely among the Holocrons the Jedi Temple had locked away, probably along with Nihilus's.
I was always under the impression that the Jedi only had a few Sith holocrons in their keeping. I think that's more or less the wording of the Episode II Visual Dictionary... though I don't know how canon that is. Until we know for certain what ended up happening to the Telos Academy, I don't think there's any way of knowing conclusively what happened to its Sith holocrons. And there were far more in Atris' chamber than we've seen in the rest of the EU combined. It increases the amount of ancient Sith knowledge still present in the galaxy... which, again, gives Krayt's order a base to build from without relying on an outside source like the True Sith.