(Possible spoilers)
This is just kind of an idea I had, spur of the moment inspiration and all. Nathema was the world where the Emperor was born and the first world he sacrificed with his ritual. Now, the ritual not only drained all life on the planet, but also essentially stripped the planet of the Force as well. My idea is that perhaps a being has formed in the void in the Force there that is born of death, and out of the lack of the Force. A being equally as powerful as the Emperor, if not more so that is kind of galaxy's balance to the Emperor's own immense Force Powers.
With my idea the Empire or the Republic would go to Nathema to face this new terrible being born of the Void in the Force that could represent the death of not only the Galaxy, but the Force as well, (Yes, this does derive some inspiration from the Exile.) Now, in ToR there's been little interaction between the supporting Lore characters of both sides in the Flashpoints and the Ops. However, in this case, this being would have such an immense power that it would require the attention of the two most powerful beings on both sides; Revan and the Emperor.
If the Republic does the Ops they fight their way through to the Anti-Force creature, for lack of a better term, and with the aid of Revan defeat it. The Empire battles through and gets to aforementioned super evil kill the entire galaxy, and the Emperor has been forced to show himself by the threat to his plans it represents, and together they kill it. Afterwards you could even potentially have a second confrontation between the Emperor and Revan, either in cinematic form or literal form. Now obviously, this would most likely take place either far down the road, (Patch 1.6) or even in another expansion.
Feel free to reply and tell me what you think of my idea, and such.