In the vast Mongolian steppe, geologist Arslan Tömör discovers a mysterious sinkhole revealing an ancient underground city called Ürgelkh ("Eternity"). Guided by Sarangerel, a teenage girl whose prophetic dreams foretold the city's emergence, and joined by Chinese archaeologist Dr. Chen, Arslan descends into a perfectly preserved technological marvel built 15,000 years ago. They discover Ürgelkh is both sanctuary and failsafe mechanism—an ark containing thousands of suspended humans (Dormants) preserved from Earth's last great ecological collapse. The city begins awakening these ancient sleepers while simultaneously initiating a programmed "Implementation"—a controlled reset of Earth's damaged ecosystems that will disrupt modern civilization but prevent total collapse.