Sverenagati is the lost capital of the serpentfolk located far below the Kodar Mountains in the Darklands layer of Sekamina. Once the center of serpentfolk culture, it is now little more than a highly dangerous ruin filled with the remnants of one of Golarion's eldest empires.1
Sverenagati, also known as the City of Coils, was built using the same magical preservative techniques used in Thassilonian construction, and many of the buildings there remain intact, despite being over 10,000 years old. Although other serpentfolk cities existed in the Darklands during the Age of Legend, none have survived to the present day.1
Over the past few centuries, the remaining serpentfolk of Sverenagati have attempted to rebuild their empire, even going so far as constructing the fortress of Viperwall in Varisia. They accessed the surface through the Mobhad Leigh, which once served as the main entrance to the ancient empire of Ydersius.1
Many different races now inhabit the ruins of Sverenagati. Its northern sections are controlled by gugs, while ropers and a large tribe of driders hold the south. Unintelligent monsters are also common and make travel through the ruins extremely dangerous.1
The center of the city is still held by the degenerate descendents of the serpentfolk, who are prone of indulging in intra-tribal conflicts and cannibalism. Every few generations a serpentfolk is born possessing the cunning and magical aptitude of their ancestors. These individuals generally attempt to unite their kind to retake their capital, but so far none have been successful.1
For additional as-yet unincorporated sources about this subject, see the Meta page.