Parlainth was the administrative center of the Theran Empire in the north-east corner of Barsaive before the Scourge. It was the greatest city in Barsaive, a marvelous great city built of white shining stone that shone far in the distance.
When they heard of the coming Scourge, the rulers of Parlainth decided that the protections offered by Thera weren't enough. Rather than build a kaer - the more common forms of protection against the Horrors - the Theran magicians cast a powerful spell that moved the entire city to a pocket dimension. To ensure that the Horrors didn't find their way to Parlainth, the Therans attempted to remove all memories of the city from Barsaive. The spell was successful, and removed not only all recollection of the city but also every record of it. As far as the people of Barsaive knew, the city had never existed. Unfortunately, it was not enough. The Horrors found the city and broke its defenses, but became themselves trapped within the city for the duration of the Scourge, growing increasingly frustrated and mad.
The ruined city eventually returned to Barsaive. There, it became a site of many treasure hunting expeditions, most of them originating in a nearby town of Haven, which arose to serve the need of the treasure hunting groups.
The city is packed with both Horrors and their minions that the Horrors created to stave of boredom when the city was trapped in another dimension. It still contains many treasures, but it is a lethal and often-time terrifying place.
Despite the dangers, Parlainth remains a tempting destination for adventurers. It is full of treasure, some of it hidden for hundreds of years, and some of it brought by other, less fortunate adventurers.