Sikong Zhen comes across mechanical beasts in the underground city and quietly studies them on his own. Wu Zetian senses that something is wrong and sends Shangguan Waner to look into it in secret, while the Yaotian organization pursues plans of its own. With these competing forces tangled together, trouble simmers beneath the surface until a shared crisis finally erupts. To protect Chang'an, everyone must push past their difficulties and join forces against the mechanical monsters. The season mixes comedy and fantasy.