In the immediate aftermath of the Beacon Cataclysm, the demon-machines still ran loose on many planets. Some worlds negotiated with the demons, others beat them back, yet more were exterminated of life, but some suffered a fate worse than death. Ûnalîar was one such unfortunate planet. The records are unclear what exactly happened, but the demonic presence was strong enough to fight off the reconquest, and repeated reconnaissance missions brought back only tales of horror. After two thousand years of quarantine, the wretched population of Ûnalîar had been driven to extinction by their cruel masters, and something had unified the monstrous demons. The Emperor of the time became concerned that they were going to become capable of interstellar travel, something that would be most disastrous.
At this point, the zaian got involved. The High Chronicler Atheran and Niren-Sûl led an elite army of Tarsins, and several thousand of their own finest warriors, to destroy the demon-machines and their shadowy leadedr once and for all. They were killed nearly to a man, and the zaian lost not only a significant and skilled part of their population, but two of their oldest and wisest of individuals, which drove them into isolation until the days of the Savior. The mission was a total failure, and whatever force was behind the demons there remained safe and undiscovered. The threat of them leaving Ûnalîar's orbit never materialized, but some have theorized that even in this remote reach of the past, they were preparing for coming of the Shadow Emperor. After the Salvation, many of the Undying and their demons fled in the direction of Ûnalîar; the mortal races did not pursue that band.
After the Salvation, Ûnalîar's existence was purged from all records and memories by the Archive in a three hundred year-long campaign; and is now watched over only by remote listening posts further out in its star system. There is travel to and from the surface, and ships from afar stop there from time to time. Whence came these ships, no one can say. The planet only appears on highly classified star charts, and all Captains in the Imperial Navy are sworn not to speak of it, and never to approach it. Whatever terrors lurk on Ûnalîar, it is best to forget them.