Sometime during her rule, Earth Queen Hou-Ting commissioned the construction of a temple as part of several extravagant expansions to the palace grounds. Following the Harmonic Convergence of 171 AG, the Earth Queen ordered the Dai Li to apprehend all citizens of Ba Sing Se who developed the ability to airbend. They were subsequently conscripted into the Earth Queen's army as part of the first airbending regiment and detained in a secret military compound underneath the temple grounds. Two weeks after Harmonic Convergence, Kai was captured by the Dai Li and sent to the facility, where he trained to develop his combative airbending abilities alongside other conscripts such as Yung.