As the Republic and the Jedi venture further into the unknown regions beyond the Outer Rim, strange events begin to occur seemingly at random. Whole ships enter hyperspace and never return, with no trace. Entire fields of crops suddenly die in the midst of an otherwise excellent growing season without explanation. People disappear without a trace, and their entire family fails to remember them. Seemingly sane people descend into madness overnight.
When Naga Sadow triggered the Cron Drift Explosion using Dark Side powers, he woke something that had been imprisoned for eons in the “space between space”, aka hyperspace. Sadow was swallowed up in the cataclysm, and consumed by the creature, the Whispering Dark. Though its prison holds, and the creature remains in a weakened state, it’s power and influence will only grow with time. By consuming the former Dark Lord of the Sith, the Whispering Dark learned about the Jedi, the Republic, and the well of dark power which lies at the heart of Coruscant. In time, it will corrupt and influence the sentient beings of the Outer Rim to feed its power, and eventually break free of its prison in order to emerge into real space and feed on enough Dark Side power to consume the galaxy.
Or something.