The start of season four sees the Qin Empire striving for tranquility and prosperity following the collapse of the Mechanical City and near decimation of the Mohists. The Emperor allocates significant resources to build the Great Wall and develop advanced programs. Nevertheless, when the colossal "Mirage" vessel unexpectedly appears offshore, the populace becomes frightened. In Shanghai, rebel guerilla factions, including Quicksand, Yin-Yang, Net Trap, and the swordsman Shengqi (aligned with the Emperor), band together and challenge the Emperor's ambitions. The Mohists, Confucianists, and Taoists unite to combat their mutual enemies. Meanwhile, as Tianming (now the Mohist leader) undergoes education and training, he faces even greater and more daunting obstacles.