Quori

The Quori are evil outsiders from Dal Quor, the Plane of Dreams. Fourteen thousand years ago, they succeeded in opening up the gates between Dal Quor and Eberron and nearly overran the world. It was only through the intervention of dragons who provided powerful magic to the giants of Xen'drik that the plane of Dal Quor was shunted away from its rotation so that it could never again become coterminous with the material plane.
The quori are no longer completely cut off from Eberron. About 1,800 years ago (-802 YK), a rebel group of 67 quori escaped Dal Quor and merged with the bodies of willing human monks of the nation of Adar on the continent of Sarlona, a continent considered to be the cradle of humanity. These quori/human mergings became a true-breeding race known as the Kalashtar.
Quori are immortal, and yet none of them know their entire history. Collectively, they have no recollection of events that occurred before the Age of Monsters on Eberron. One possible explanation for this, and the explanation that is believed by the Quori themselves, is that Dal Quor itself undergoes cataclysmic cycles. When the cycle turns, what the Quori refer to as the "Turning of the Age", the plane implodes and explodes. The Quor Trai (spirit of the age) is reborn in a new form, and all other quori spirits are pulled into this cataclysmic metamorphosis and reformed anew. Dal Quor, and the quori, will always exist in some form, but the quori of the future could have absolutely nothing in common with the quori of the present day.
One of the wisest of the quori was a kalaraq named Taratai. Taratai believed that il-Lashtavar would be replaced by il-Yannah, a great light that would banish the nightmares and transform the quori into spirits of light. Taratai led the group of rogue Quori that became the Kalashtar.