Siöl was once the largest, most populous and most powerful Nonman Mansion. It was located in the Great Kayarsus Mountains, north of the Sea of Cerish, from where its Reach extended across much of north-eastern Eärwa. A thousand years before the Breaking of the Gates, it's king was Cû’jara-Cinmoi, the greatest of the Nonman Kings.
Siöl was already mighty when the Incû-Holoinas fell from the skies into the south-western peaks of the Yimaleti Mountains, devastating the lands controlled by Nin’janjin, the King of Viri. Nin'janjin pleaded for aid but Cû’jara-Cinmoi instead invaded and occupied his lands. Faced with famine and starvation, Nin'janjin surrendered without offering battle; Viri became a bloodless tributary of Siöl. Cû’jara-Cinmoi then conquered the mansions of Nihrimsul - where her King, Sin’niroiha (“First Among Peoples” in Ihrimsû), was forced to wash the sword of Cû’jara-Cinmoi - and Cil-Aujas. This extended the Reach of Siöl as far west as the Yimaleti and Demua Mountains and south to the shores of the Meaneanor Sea, creating one of the largest land empires in the history of Eärwa. Cû’jara-Cinmoi proudly styled himself the "King of Four Mansions"; after the successful rebellion of Nihrimsul he reluctantly adjusted this to "King of Three Mansions".
During the Cûno-Inchoroi Wars, Siöl suffered serious losses in battle, as well as the loss of its entire female population. The Mansion survived the wars - although the records are confusing - but it was then destroyed in the Cûno-Halaroi Wars that followed the Breaking of the Gates. Indeed, some hold that the Gates and Siöl are one and the same, and the destruction of Siöl heralded the arrival of Men in Eärwa.
Siöl claimed to be the First Mansion, the ancestral home of all Nonmen, founded directly by the progenitors of the Nonmen race in a time so ancient as to defy reckoning. For this reason Siöl took the title "House Primordial", a term used to refer to both the Mansion and its ruling family. Extant records support this, tracing a line of founding from Siöl to first Ishoriöl, Viri, Illisserû, and Cil-Aujas. Those Mansions turn later founded Curunq, Incissal, and Cil-Aumûl. Nihrimsul was founded separately and outside of this line of descent, although its claim to have originally founded Siöl (and thus being the true House Primordial) was hotly denied by Siöl.