The Avatar is the spirit of the planet incarnated in human form and thus, the only physical being with the ability to learn all four bending disciplines. It is considered the Avatar's duty to master the four elements and use such power to keep balance among the four nations of the world. With the death of the Avatar, the spirit is reborn into the following nation, dictated by the cyclic order; water, earth, fire, air. Coincidentally, the cycle of reincarnation corresponds to the cycle of the seasons; each of which is affiliated with a particular nation and element; water and winter, earth and spring, fire and summer, air and autumn. The cycle is also the traditional order in which any one Avatar is to master the elements, beginning at whichever element they were born into. The cycle can only be broken if the Avatar dies while using the Avatar State.
The Avatar possesses an innate connection to the Spirit World and uses it as a bridge by which to reconcile the two worlds and ensure harmony. The Avatar is also capable of using this ability to contact the spirits of previous Avatars and harness their combined energy to perform feats of bending beyond that of any other bender. Throughout the ages, countless incarnations of the Avatar have served to maintain harmony in the world.
Each nation has a method of recognizing the new Avatar. Among the Air Nomads, this involved presenting all infants with a selection of toys to play with and watching for a child that selected four specific toys that had belonged to past Avatars, called the four Avatar relics. Traditionally, the child is told of his identity as the Avatar on his sixteenth birthday. In places like the earth kingdom and Fire bending the avatar is found after the child is drawn to specific areas they had been before in their past lives. However, Avatar Aang was told much earlier than this because of Fire Nation aggression.
The Avatar also possesses the ability to bend energy, though very few Avatars have learned this technique, and even fewer have used it. When the Avatar masters control of the Avatar State, they are commonly said to be a 'Fully Realized Avatar'. However, it has not yet been confirmed whether mastery of the four elements, namely water, earth, fire and air, is required for this status as well.
The first Avatar, Wan, became the Avatar after he tried to settle affairs between the humans that lived in his time and the spirits. His actions set into motion the chain of events that led to the Avatar Cycle.The reincarnation of the Avatar is controlled by the Avatar Cycle of the elements: water, earth, fire, air. The cycle is based on the passage of the four seasons (water is winter, earth is spring, fire is summer, and air is autumn).
When an Avatar dies, the next Avatar will be born into the next nation in the Avatar Cycle; for example, Avatar Yangchen from the Air Nomads was followed by Avatar Kuruk from the Northern Water Tribe, who was followed by Avatar Kyoshi from the Earth Kingdom, who was followed by Avatar Roku from the Fire Nation, who was followed by Avatar Aang from the Air Nomads.
The Avatar Cycle also determines the order in which each Avatar must learn the four bending disciplines. The Avatar begins by mastering his/her native element, so an Avatar born into the Water Tribe would first learn waterbending. The Avatar then goes on to learn the three remaining bending disciplines in the order of the cycle; the Water Tribe Avatar would first learn waterbending, then earthbending, then firebending, and finally airbending, in that order.
The known Avatars in the order of current to oldest are:
- Kyoshi (Earth Kingdom, now Kyoshi Island)
- 312 BSC - 82 BSC
- Creator of Kyoshi Island
- Longest living Avatar
- Founder of the Dai Li
- Before 10,000 BSC
- First Avatar
- "The Avatar State is a defense mechanism, designed to empower you with the skills and knowledge of all the past Avatars. The glow is the combination of all your past lives, focusing their energy through your body. In the Avatar State, you are at your most powerful, but you are also at your most vulnerable. If you are killed in the Avatar State, the reincarnation cycle will be broken and the Avatar will cease to exist."
The strongest and most powerful ability that the Avatar can invoke is the Avatar State. It allows the Avatar to channel cosmic energies and the knowledge of previous Avatars, enabling them to perform especially powerful and extraordinary bending feats. The Avatar may unconsciously enter the state in response to perception of mortal danger, utilizing the state as a defense mechanism, or emotional distress. While in the state, the Avatar has access to bending techniques they themselves may not have yet learnt, but have no conscious control over their actions and can cause great collateral damage. An Avatar with full mastery of the Avatar State has conscious control over the state and can enter and exit it at will. For an Avatar with complete mastery, their eyes will glow momentarily, not continuously.
While in the Avatar State, the Avatar's eyes glow, as do any markings following chi paths along the body, such as Air Nomad tattoos; however, if the body has received an injury deeper than the tattoos, then that specific area will not glow in the state. The glow is the combination of all the Avatar's past lives, focusing their energy through a single body. When the Avatar speaks in the Avatar State, their voice encompassed a combination of several different voices at once.
It is possible for an Avatar to control the Avatar State, as Aang, Roku, Kyoshi, Kuruk, Yangchen, and Miru have demonstrated in numerous flashbacks, but this requires great spiritual discipline and concentration. More often, the Avatar State is activated by danger or emotional turmoil, being called a defense mechanism. When an Avatar is in complete control of the Avatar State, their eyes glow momentarily, not continuously.
It is possible for an Avatar to channel a specific previous incarnation while in the Avatar State. When this happens, the Avatar briefly takes on the appearance and voice of that previous incarnation. Aang did this on several occasions with multiple Avatars. It is unlikely the age of the Avatar's death is the deciding factor in their appearance since Avatar Kyoshi lived for 230 years and would not have kept a young appearance at that time. It is possible that those in the Spirit World manifest visually as they see themselves and not as they currently are. The Avatar State is also capable of nullifying the effects of bloodbending.