Set in the mythical land of Arth, the story follows the inhabitants of the ancient city of Arthdal and its surrounding regions. As the city grows into a powerful nation, power struggles emerge between those who seek to build a new civilization and those who wish to protect the old ways. The narrative centers on Eun-seom, a young man born with the destiny of bringing disaster to Arthdal, and his journey to save his tribe while uncovering the secrets of his mysterious origins. As the ambitious Tagon, a war hero and leader of the Saenyeok Tribe, maneuvers to seize control of the city, he clashes with the interests of the Wahan Tribe and the mysterious Neanthals. The series explores themes of tribal politics, the birth of religion, and the complex morality of leaders striving to forge a unified empire in a world defined by ancient prophecies and supernatural forces.