Which episode is listed as episode 30 overall?

The episode listed as episode 30 overall is “The Library,” the tenth chapter of Book Two: Earth.

In the episode, Team Avatar travels into the Si Wong Desert after Professor Zei tells them about a legendary spirit library. Sokka hopes its records will reveal a weakness in the Fire Nation. Inside, the group meets Wan Shi Tong and discovers information about a solar eclipse, which later becomes central to the invasion plan on the Day of Black Sun.

“The Library” also begins one of the series’ most painful story turns. While Team Avatar is inside, sandbenders capture Appa. Toph holds up the sinking library long enough for the others to escape, but the group leaves without him. The next episode, “The Desert,” follows their journey across the desert after the loss.

The alternatives are nearby Book Two episodes. “Bitter Work” is episode 29, “The Desert” is episode 31, and “The Drill” is episode 33.