Energybending



In "Sozin's Comet, Part 4: Avatar Aang", Aang uses Energybending to strip Phoenix King Ozai of his Firebending.

History
After discovering that the mysterious island on which he consulted his past lives was in fact a Lion Turtle, he consulted the ancient creature on what he should do about Ozai. He asks for wisdom on how to stop the Fire Lord without taking his life.

The Lion Turtle answers, "The true mind can weather all lies and illusions without being lost. The true heart can touch the poison of hatred without being harmed. From beginningless time, darkness thrives in the void, but always yields to purifying light". The Lion-Turtle brings up a paw, his two claws touching Aang's chest and forehead, causing a green light to illuminate. Thus granting Aang the ability to Energybend.

Aang doesn’t understand at first, but is comforted by this wisdom. During the battle with Ozai, Aang is in the Avatar State, and with the combined power of the past Avatars and all the elements, the Avatar is ready to deal the final blow. At the last second, Aang gains control and exits from the Avatar State, deciding not to end the Fire Lord's life. Ozai says that even though he has all the power in the world he is still weak and attempts to attack Aang, who senses the attack with Toph's Earthbending detection technique, and pins Ozai down again. In this moment, he realizes the meaning of the advice of the Lion Turtle, and he decides to act on it.

The Lion Turtle told him that in the era before the Avatar existed, the benders did not bend the elements, but life energy itself. In order to bend another's life energy, their own spirit must be unbendable, or they would be corrupted and destroyed.

It is Aang's "true heart" and "true mind", tested in the heat of battle at the moment of striking down Ozai, that allowed him to harness the wisdom of the Lion Turtle and successfully Energybend Ozai.

When Aang was Energybending Ozai, his entire body was shining white and blue, while Ozai's body shined orange and red. At first Ozai's spirit enveloped Aang almost completely, but at the last moment, Aang's spirit took over. Eventually, Ozai's body was enveloped by Aang's shining spirit, and Ozai lost his bending skill. Very few Avatars ever learned Energybending, and even fewer ever used it.

Dangers of Energybending
Energybending is an extremely powerful but also an extremely dangerous technique. If the bender's spirit is even slightly weak (bendable) then they will be infected by the spirit of the one they are bending. As a result the bender can be corrupted and even killed.

Trivia

 * The chanting that can be heard while the Lion Turtle speaks to Aang explaining how to Energybend (also when the Lion Turtle first called Aang to sleepwalk/swim to him) is a Buddhist chant "Na Mo A Mi Tuo Fo" (spellings vary).
 * At a Comic Con panel in July 2008, Mike and Brian jokingly name this type of bending "Anti-bending" and "Un-bending," since it was never given a name in the series, referring to the ability stripping a person of their bending.
 * While unnamed in the series, the term Energybending comes from Nick.com, and therefore considered canon.
 * At the last sec. Aang's head aimed at Ozai so the beam of light may have affected Ozai's spirit.