The Avatar
The Avatar is the spirit of the planet reincarnated in human form. He is able to master all four elements and it's his or her job to maintain balance and peace between the four nations. At one time, there can only be one Avatar, but upon his or her death, the Avatar Spirit is reincarnated in a baby from the next nation in the cycle. That baby will become the new Avatar.
The Avatar Cycle is Water, Earth, Fire and Air. This pattern follows the changing of the seasons (Winter, Spring, Summer, Fall) and provides balance to ensure that one nation will not become more powerful than another. The new Avatar is typically born a week after the previous Avatar's death and he or she tends to select the same toys the previous Avatars played with. Traditionally, the new Avatar wouldn't be told his identity until his sixteenth birthday.
Much of the Avatar's power stems from his ability to master all four elements. The training starts off with the mastering of his or her native element and then goes on to the next element in the cycle. Since the Avatar has mastered the elements countless times through countless lifetimes, they tend to be very gifted. When he or she has mastered all four elements, they become a Fully Realized Avatar.
Another unique ability the Avatar has is the ability to communicate to the Spirits. He or she is the bridge connecting the human world to the Spirit World. Past Avatars reside in the Spirit World and they can provide mentorship and advice to the new Avatar.
As a defence mechanism, the Avatar can enter into the Avatar State, which provides them with power of all the previous Avatars. They are able to perform extraordinary feats such as freezing their body for over 100 years or activating a volcano. Their eyes glow white and in the case of Air Nomads, the tattoos also glow. The glow is the combination of all the past lives, focusing their energy through the body.
While in the Avatar State, the Avatar is at his most powerful, but also at his most vulnerable. If the Avatar is killed while he's in the Avatar State, the Avatar cycle will be broken permenantly. That means that the Avatar will cease to exist.
Notable Avatars
Avatar Aang is the protagonist in the series. He was born during a time of great conflict and was thrust into his role as the Avatar at a much earlier age than most. He disappeared for 100 years in which time, the Fire Nation had wiped out all of the Air Nomads and were making progress conquering the rest of the world. His duty is put a stop to the war before Sozin's comet arrives, which will grant the Firebenders unlimited power.
Avatar Roku was the Avatar before Aang. He becomes a mentor to Aang and taught him about the Avatar's abilities and responsibilities. Roku grew up as a citizen of the Fire Nation and was bestfriends with the crown Prince Sozin. When Sozin became the Fire Lord and began to colonize Earth Kingdom towns, Roku was not decisive enough and did not put a complete stop to the rebellion. He blames himself for not putting an end to the war early on.
Avatar Kyoshi was born in the Earth Kingdom and was the Avatar before Roku. She lived to be 230 years old and had the largest feet of any Avatar. Kyoshi had no qualms about killing enemies to achieve peace. She formed the Kyoshi Island which used to be attached to the Earth Kingdom. The Kyoshi Warriors adopted her wardrobe, face paint and her steal fan weapons. Kyoshi was an effective Avatar, but she was the founder of the Dai Li, a decision that she regrets.
