"I've also learned the Emperor is on Dromund Kaas. His efforts against us have weakened him. Our enemy is vulnerable—for now. The Emperor is determined to destroy the galaxy. It's him, or us." "You must face the Emperor again. And this time, you cannot fail."
"I will not be contained I cannot be redeemed. Death is all that remains, and you will not kill me." "I don't want to kill you—but you will face justice for your crimes." "There is no justice. There is only... revenge."
Confronting the Sith in the Temple, the Knight defeated the Emperor and killed his current Voice, the body that he was possessing. The Sith Emperor, while still alive, was severely weakened, and hid his survival from the Jedi and his spirit fled the citadel to rest and recover. Parts of the citadel were damaged in the battle, when Vitiate tried to bring the ceiling down on his foe.
The Dromund Kaas operation first appeared in the Jedi Knight class's finale mission "Doomsday" in Star Wars: The Old Republic, a video game released by BioWare and LucasArts in 2011. The mission is identified as the "Dromund Kaas operation" by the droid RL-4, who introduces the Karagga's Palace Operation for Republic players, and the events of the Operation are revealed to have been directly influenced by the death of the Emperor in the Operation Explosive Conflict. The Dread Masters' recent expansion into Hutt Cartel territory and their actions on Denova are a result of the Emperor's "death", as he no longer controls them and they decide to become independent—thereby setting up the events of the Karagga's Palace, Explosive Conflict, and Terror From Beyond Operations.
↑A holomessage to the Emperor's Wrath from one of the Emperor's Hands confirms that the Emperor was defeated by the Knight "while you were dealing with Baras", confirming that the two duels were concurrent.