When Team Avatar arrived at Crescent Island, the Great Sage, along with the other Fire Sages, attacked the group. Their attacks were in vain, as they were knocked down by an air swipe directed at them by Aang. The Great Sage was fearful of how powerful Aang would become if he would succeed in his endeavor to contact Roku, so he ordered the others to split up and find the Avatar.
The Great Sage was later tricked by Aang and his friends with the help of Shyu into opening the Fire Temple's sanctuary, which housed Avatar Roku's statue. When he realized his mistake, he tried to close the door again, but was thwarted by Momo, who jumped on his face, eventually removing his headgear. When Zuko intervened and captured the Avatar, the Great Sage nearly succeeded in his attempt to stop Aang from speaking to Roku. However, at the last moment, Aang broke free and used the Great Sage's head as a stepping stone to jump through the closing doors of the sanctuary. When he tried to open the door again, he realized that Avatar Roku did not want them to enter, and had thus sealed the door shut.
Unable to do anything about the situation but wait, the Great Sage started to interrogate Shyu in order to comprehend the motive behind his actions. During this interrogation, CommanderZhao entered the temple. The Great Sage bowed to him in respect, showing his loyalty to the Fire Nation above his original loyalty to the Avatar.
When Aang emerged, serving as a vessel for Avatar Roku and burning the entire temple to the ground, the Great Sage fled to safety with the others. After Zhao held him and the other sages prisoner and accused them of treachery, the Great Sage argued that only Shyu had aided the Avatar. Zhao, however, was unfazed and turned them in to Fire Lord Ozai to be punished for their alleged crimes.