Avatar Kuruk was the Water TribeAvatar immediately succeeding Avatar Yangchen and preceding Avatar Kyoshi. Native to the Northern Water Tribe, he was born around 340 BSC and died in 312 BSC. Throughout his short life, Kuruk was a gifted though brash and arrogant person, who always preferred a "go with the flow" kind of mentality. Due to this attitude and his pompous demeanor, Kuruk lost his fiancée, Ummi, to Koh the Face Stealer.
Living in a world brought to peace and stability by his predecessor's tenacious efforts, Kuruk spent most of his days searching both the physical and Spirit World for worthy opponents to challenge in bending contests, usually for no other reason than for the fun of it. He also liked showing off grand displays of his bending ability to others, especially beautiful women. Kuruk airbent lotus tornadoes for young Air Nomad nuns, challenged random Fire Nationcitizens to an Agni Kai, and engaged in earth-lifting contests with earthbenders. His strength in sparring matches was considered legendary, and no bender was ever able to trump his abilities. Kuruk was a "go with the flow" type of Avatar. The world's tranquility allowed him to step back from his responsibilities as the Avatar and let the four nations resolve their own conflicts. Although there was peace, Kuruk's carefree lifestyle would eventually cost him dearly.
Never having even the slightest thought of settling down, Kuruk carried on with his casual way of life until the day he met his true love. At the New Moon Celebration, a festive meeting of the two Water Tribes, he met a woman named Ummi from the Southern Water Tribe. Kuruk fell in love with her at first sight and presented Ummi with a customary betrothal necklace shortly after their meeting, which she accepted. The two designated their marriage to be at the Spirit Oasis.
As they approached the altar on the night of their wedding, Ummi fell into the oasis, pulled in by an unseen force. She had been lured to the Spirit World by Koh the Face Stealer, to punish Kuruk for his past arrogance. Every year, on the anniversary of their wedding, Kuruk traveled to the Spirit World in hopes of saving Ummi, but failed on every occasion. His attempts made Koh hold a grudge against the Avatar. Kuruk continued the search for his wife even after his death. After he received information on Ummi's whereabouts during a brief encounter with Avatar Aang, he once again confronted Koh. He eventually managed to find Koh and proceeded to slay him, but was unable to as the spirit had stolen Ummi's face and trapped her forever, preventing Kuruk from killing Koh without killing his wife in the process.
Aang first learned about Kuruk while he was in the Spirit World during the Siege of the North. Koh informed him that Aang had attempted to slay him in a previous incarnation, though the spirit never specifically identified this man as being Kuruk.
Later, while Avatar Roku was teaching Aang about the Avatar State, Aang briefly envisioned Kuruk performing advanced waterbending.
Aang finally learned Kuruk's name when he was in a coma after Azula's lightning attack in Ba Sing Se. When they met in the realm of Koh, Kuruk asked Aang if he had seen a beautiful woman with long, brown hair. Aang responded by inquiring about Kuruk's dilemma, at which point Kuruk proceeded to tell him his history as the Avatar. After the tale, Aang realized that during his encounter with Koh, one of the spirit's faces was that of the woman Kuruk had described. Heartened by the knowledge of where his wife was, Kuruk set off to track down Koh once again. However, as Avatar Yangchen had predicted, Aang retained no memory of this encounter.
Later, Avatar Aang meditated on contacting Kuruk's spirit to ask him how he could defeat Fire LordOzai without killing him. Kuruk told Aang to actively shape both his destiny and the destiny of the world, as he failed to do so in his own life. It was Kuruk's own arrogance and inaction that cost him his beloved wife, Ummi. Aang took this to mean that Kuruk, like the other Avatars, believed it was necessary to use lethal force in order to protect the world. However, Kuruk's answer was much more open to interpretation, since "actively shaping your destiny" could have various meanings, including Aang's decision to strip Ozai of his bending.
Kuruk stood alongside all the other Avatars when Aang passed on the knowledge of energybending to Korra and restored her bending, representing the newly established connection she made to her spiritual self.
In the last episode of the series, Kuruk was seen in Aang's vision before he entered the Avatar State.
During his airbending training, Avatar Kuruk was seen with a customized Air Nomad uniform that was similar to Aang's, but in varying shades of blue.
Kuruk is the Pawnee Native American word for "bear", mimicking how Kuruk is frequently seen wearing an animal pelt resembling a bear-like creature over his head.
Koh stated that Kuruk attempted to slay him some eight or nine centuries prior to the episode, but for that to have happened, he would have had to be older than his immediate successor, Avatar Kyoshi, who was the oldest Avatar in history.
Kuruk's favorite mode of transportation was by sea, surfing on a raft using waterbending.
Kuruk is, so far, the only known Avatar whose predecessor and successor were bothwomen.
Among all Avatars with a known lifespan, Kuruk lived for the shortest period of time. Ironically, his successor, Kyoshi, lived longer than any other Avatar.