|Tenzin was having trouble managing his new airbending apprentices, and Boomy turned out to be better at being a leader and getting them motivated..|
Meanwhile, the bad guys broke into the metal-bending city and almost succeeded at capturing Korra. These 4 guys combined are stronger than the avatar. The earth bender can even lava-bend. They escaped, and team avatar started going to track them down.
Korra went into the spirit world and found Zahir, but Zahir didn't want to fight since neither of them can bend anyway. Zahir agreed to talk with her and tell her about their group and motivations. They are called "The Red Lotus", a group that broke off from "The White Lotus" from the previous series. These guys were in cahoots with Korra's uncle in the previous season, but the whole dark avatar thing wasn't part of their plans. They basically want to restore balance to the world in their own way.. they want to bring down the whole concept of nations and governments and put the world back to its original form of pure chaos.