Ok, just to clarify what happened in my post:

-Yerbol had visions of the "Heralds" and their subsequent eradication by the Sith from the Old Republic era. The knowledge was locked away in the tombs. 

-The scrolls contain the history of the Heralds and their downfall as charted out by Sith historians. 


I'm thinking this about the Heralds. Let me know what you think:

-The Heralds were an advance part of scouts and diplomats that emerged from Wild Space, "heralding"(eh? eh? xD) the return of the "True Sith". 

-The Heralds demanded full control of Korriban and the Empire, proclaiming that their masters were the ones who should decide the fate of the Sith, not "pretenders"

-The Sith killed the Heralds due to the power grab and sealed their knowledge away. Their knowledge is so dangerous to the Sith because it reveals a path in between the Light and the Dark. Essentially, the "True Sith" practiced staying "balanced" and not allowing either light or dark to commandeer their thinking. 

What do you think? 

Also, forgive me if the quality of ideas are off. I'm feeling horrendous at the moment due to some illicit food poisoning xD