The Nightmare War
The Dreaming Dark
Information as explained by Shemhazai in Episode 10
Officially, the Dreaming Dark does not exist. Most people in Riedra have never heard of it, and never will. The Dreaming Dark is the ultimate power behind the quori - ultimately, all quori serve the Dreaming Dark, though a select few have managed to resist their influence and power. It has agents throughout all of Sarlona's organizations. Most of its agents operate outside of Riedra, in the rest of Sarlona, but also in Xen'dric and especially Khorvaire as of late. Agents of the Dreaming Dark are mainly Inspired Chosen, though they use mind seed to subvert members of other races. The overlord of the Dreaming Dark is called The Devourer of Dreams.
It is said that the Dreaming Dark's ultimate goal is to maintain il-Lashtavar, the current state of Dal Quor, and to do so it must control the dreams of all beings on Eberron that can dream. Within the past 1,200 years, they've managed to control the dreams of nearly an entire continent – only Adar and a few other remote places remain free from their influence. Though they do not officially exist, they are the true power behind Riedra. Those Chosen families bred to become members and hosts of the Dreaming Dark are called the Shadow Lines.