If I am to understand correctly, this is the background of the Dark Temple: The Dromund System, including Dromund Kaas, was discovered and charted by Tulak Hord, who was the Dark Lord of the Sith at some time prior to Marka Ragnos and he had a Sith named Lord Pharshol oversee its construction in the middle of the jungle world where it was the only thing built at the time. At some point out of fear of his success, Tulak Hord had his top General Aloysius Kallig (the Inquisitor's ancestor) assassinated and buried in the tomb. A combination of unrest caused by Kallig's spirit and the good old motive of Sith rivalry led to the overseers of the temple turning on each other, with Pharshol facing and defeating another Sith named Lord Vacuus who wanted his position. A group known as the 'Dark Path' also rose up and most likely convinced Pharshol's apprentice Anyarah to betray him. They all eventually killed each other and/or died off and the temple and planet's location were lost to history. Through the Dark Side and possibly as a result of the ritual performed on Medriaas/Nathema, Emperor Vitiate rediscovered the location of Dromund Kaas and eventually led his people there. After appointing a Dark Council, he had several of his allies--including Nil Venerous, Keleth Ur, and Barrel Slathborn--killed and buried in the temple where their spirits were sealed inside tombs, but Kallig's spirit which was already there caused unrest and these spirits possessed the members of an archaeological expedition that had been sent in there to gather readings for structural integrity. Another team was later sent in with a blowtorch to seal the tombs but also failed and was likely possessed.

Did I miss anything?