Sixteen-year-old Sokka and his fifteen-year-old sister, Katara, are near a river at the Southern Water Tribe, a small village in the South Pole. While hunting, they discover an iceberg that when broken open shoots a beam of light into the sky. Inside of the iceberg is a thirteen-year-old boy named Aang and a giant flying bison named Appa. Unknown to them, Aang is the long-lost Avatar â the only person capable of "bending" all four elements of Air, Water, Earth, and Fire. One hundred years have passed since the Fire Nation has declared war on the other three nations of Air, Water, and Earth in their attempt to conquer the world.Zuko is the scarred seventeen-year-old exiled prince of the Fire Nation on a quest to find the Avatar and bring him to his father, Fire Lord Ozai, so he can regain his honor. Seeing the light that appeared from Aang's release, Zuko and some Fire Nation soldiers arrive at the Southern Water Tribe to demand the villagers hand over the Avatar. Aang reveals himself and surrenders to Zuko on the condition that he agrees to leave the village alone. On the ship, Aang is tested by Zuko's paternal uncle Iroh to confirm he is the Avatar. After being informed that he is to be their prisoner for passing the test, Aang escapes using his glider and flies to his flying bison brought by Katara and Sokka. Aang and his new friends visit the Southern Air Temple where they meet a winged lemur, who Aang later names Momo. Aang also learns that he was in the ice for a whole century and that the Fire Nation wiped out all of the Air Nomads, including his guardian, Monk Gyatso. In despair, he enters the Avatar State and finds himself in the Spirit World where he encounters a Dragon Spirit. Katara's pleas bring Aang back out of the Avatar State.To seek shelter, Aang's group arrives at a little Earth Kingdom village controlled by the Fire Nation, but are arrested and taken to a prison for Earthbenders surrounded by earth [12] because Katara tries to help a young boy escape from Fire Nation soldiers. They incite a rebellion by reminding the disgruntled earthbenders that Earth was given to them. Aang tells Katara and Sokka that he only knows airbending and must master the other three elements. Katara is given a waterbending scroll that she uses to greatly strengthen and hone her waterbending abilities and to help Aang learn as they make their way to the Northern Water Tribe (where Aang will be able to learn from waterbending masters) and liberate more Earth Kingdom villages in the process, weakening the Fire Nation's food and water supplies.During a side track to the Northern Air Temple on his own, Aang is betrayed by a peasant and captured by a group of Fire Nation archers, led by Commander Zhao, a Fire Nation Commander appointed by the Fire Lord. However, a masked marauder, the "Blue Spirit", helps Aang escape from his imprisonment. Zhao realizes that Zuko is the masked vigilante. He arranges to kill the prince, but Zuko survives the attempt on his life with Iroh's help. He sneaks aboard Zhao's lead ship as his fleet departs for the Northern Water Tribe, which is a heavy fortress, to capture the Avatar. Upon arriving, Aang's group is welcomed warmly by the citizens of the Northern Water Tribe. Sokka quickly befriends the Northern Water Tribe princess, Yue. After a few agreements, a waterbending master, Pakku, teaches Aang waterbending. Katara also becomes a much stronger and more powerful waterbender due to her training with Master Pakku.Soon, the Fire Nation arrives and Zhao begins his attack while Zuko begins his search for the Avatar on his own. After defeating Katara in a battle, Zuko captures Aang as he enters the Spirit World to find the Dragon Spirit to give him the wisdom to defeat the Fire Nation who tells him to let his emotions "flow like water". Returning to his body, Aang battles Zuko before Katara freezes him. Before leaving to join the battle, Aang lowers the ice so that Zuko can breathe. As the battle escalates, Iroh watches Zhao capture the Moon Spirit, with which its Ocean Spirit counterpart had assumed the form of a fish. Despite Iroh's pleas, Zhao kills the Moon Spirit to strip all of the waterbenders of their ability to waterbend. Yue explains to everyone that the Moon Spirit gave her life, willing to give it back as she dies in the process. With the tables turned, Zhao finds out Zuko survived. They almost fight before Iroh appears and tells Zuko it's not worth it. Zhao is drowned by waterbenders after Zuko and Iroh leave him to his fate. Aang remembers his life before being trapped in the ice, including when he left his home, seeing his master's face. With his waterbending powers and his emotions "flowing like water", Aang enters the Avatar State and raises the ocean into a gigantic wall to drive the armada back. Aang now fully embraces his destiny as the Avatar as he, Katara and Sokka prepare to continue their journey to the Earth Kingdom to find an earthbending teacher for Aang. The Fire Lord learns of the defeat; angry over the betrayal of his brother Iroh and the failure of his eldest son Zuko, he tasks his youngest daughter Azula (and Zuko's sister) to stop the Avatar from mastering Earth and Fire before the arrival of Sozin's Comet.
Output: Question: What are the four nations?, Answer: Fire, Air, Water, and Earth