Unalaq

"You think what Avatar Wan did was good? Driving almost all the spirits from this world? The Avatar hasn't brought balance, only chaos. You call yourself the bridge between the worlds, but there shouldn't be a bridge. We should live together as one."

- Unalaq to Korra, reflecting his true motives

Unalaq is the main antagonist of Book 2: Spirits in the Legend of Korra, before the Dark Spirits, and after Vaatu. He was Korra's uncle, the younger brother of Tonraq (Korra's father), and the father of the twins Desna and Eska. Though initially Unalaq seemed to be a well-meaning individual who offers to train Avatar Korra in the ways of the Spirits, his villainous side was revealed when it's learned that he was the one responsible for the banishment of his brother Tonraq from the Northern Water Tribe. His villainy becomes even more apparent when it is revealed that he is working for Vaatu. He was also the first (and only) Dark Avatar for a day.

Past
Unalaq was the second child to be born to the Chief of the Northern Water Tribe, his brother Tonraq being the first. As he was growing up, Unalaq took a fascination towards the Spirits, as well as their ways. It was also revealed that Unalaq was always jealous of his older brother, Tonraq, and that he wanted to become the Chief of the Northern Water Tribe. So to become next in line, Unalaq devised a plan to get his brother banished. Unalaq hired a small army of Barbarians to attack the Northern Water Tribe. After the Barbarians managed to get Tonraq's attention, they were to retreat to a Spiritual Forest, to which Tonraq destroyed the forest to find them. Later that night, after Tonraq captured the Barbarians, angry Spirits attacked the Northern Water Tribe. With his knowledge of the Spirits, Unalaq managed to subdue all of them with ease. Afterward, Tonraq admitted to his mistake. Enraged, the Chief of the Northern Water Tribe, their father, banished Tonraq to the Southern Water Tribe. With his brother banished, Unalaq became next in line to become Chief of the Northern Water Tribe.

As years went by, Unalaq eventually became the Chief of the Northern Water Tribe, got married, and eventually had two kids, the twins Desna and Eska. Unalaq eventually found out that his brother was the father of the latest Avatar; Korra. So Unalaq joined an organization known as the Order of the Red Lotus, an organization that opposed the Order of the White Lotus for becoming servant to the Avatar. There, he met four other members; Zaheer, Ghazan, P'Li, and Ming-Hua. Unalaq assigned the four to capture the Avatar so he could undo what Avatar Wan did many years ago. The four failed and ended up getting captured by Fire Lord Zuko, Tenzin, Tonraq, and Sokka. To prevent anyone from knowing that he was involved with the attempted kidnapping, Unalaq assisted with Firelord Zuko with the detainment of P'Li, and the creation of a top secret prison in the Northern Water Tribe.

Becoming Korra's Teacher
Six months after Korra defeated Amon, Unalaq and his children came to visit his family at the Southern Water Tribe, while attending the Glacier Spirits Festival. He stated that he was disappointed on how the Southern Tribe forgotten about the Spirits, and certain traditional ways. During the Festival, Unalaq was attempting to convince Korra to be his student so he could teach her about the spirits, how to tame angry Spirits, and the Spirit World. But both Tenzin and Tonraq didn't want her to be taught by him. That night, an Angry Spirit attacked the festival. Korra and her friends were proven to be no match for the Spirit, but then Unalaq appears out of nowhere and managed to tamed the spirit. Impressed by Unalaq, Korra accepted his offer, much to her father's disapproval. Unalaq told Korra that in order to calm the Spirits, they would have to journey to the Everstorm to restore the Southern Lights. After a while, Unalaq, Korra, her friends and Tonraq reached the Spiritual Forest. Unalaq explained that she was the only one who could enter the forest and unlock the spirit portal.

Controlling the Southern Water Tribe
After Korra successfully unlocked the portal between the Human World and the Spiritual World, Unalaq told her that it wasn't over yet. The next morning, Soldiers of the Northern Water Tribe arrived at the shores of the Southern Water Tribes. Unalaq told Korra that more work needed to be done before the two tribes could truly be reunited again. While they were discussing this, the soldiers created blockades to prevent any citizen of the Southern Water Tribe from escaping, nor for anyone to enter the South Pole. This caused tension between the North and the South to point where there have been rumors of war. Unalaq stated that all of this was necessary to unite the two tribes. One night, Southern Rebels attacked Unalaq in his sleep and attempted to assassinate him. Korra managed to rescue her uncle and capture all of the rebels. At first Unalaq was considering banishment for their crime, but Korra recommended a trial to the assassins, to which Unalaq agreed. The next morning however, Unalaq, along with a small group of Northern Water Tribe Soldiers appeared at the door of Korra's home. Unalaq stated that Tonraq and Senna, Korra's mother, were under arrest for attempted assassination.

The Trial
Korra's parents and the Southern Rebels were put on trial. Unalaq told Korra that he personally hired the "fairest" judge he could find; Judge Hotah. Despite this, all except for Senna were found guilty for the act of treason, and the crime for treason is punished by death. Enraged, Korra threatened to kill the judge if he didn't change the sentence. With that gesture, Unalaq managed to "convince" the Judge to reconsider the sentence. With that, Hotah lowered the sentence to life in prison.

Unalaq Revealed
Later that day, Korra chased down Hotah and confronted him. He told her that the trial was rigged by Unalaq. He also told her that Unalaq did this so he could earn Korra's trust and get his brother out of their way. Hotah even said that Unalaq was responsible for Tonraq's banishment in the first place. After finding out, Korra and her friends went to Tonraq's prison cell to break him out, only to find out that his cell was empty. Just then Unalaq appeared and told her that both Tonraq and the rebels were sent away, via a ship heading to the north. Confronting Unalaq about his selfish and underhanded deeds, Korra renounced him as her teacher and demanded that he recall the prison ship, reminding him that he still needed her to open the northern spirit portal. However, Unalaq confessed that he no longer needed her, revealing he had only been exploiting her into thinking that. This caused the Avatar to attack him out of sheer anger and fury. Both Korra and Mako confronted Unalaq, but Unalaq proved to be a powerful waterbender. After a while, Korra unleashed a powerful gust of wind to push Unalaq back. With that distraction, Korra and her friends ran off to save Tonraq and the rebels.

However, it was revealed that Unalaq still needed Korra to open the northern spirit portal. So he sent Eska and Desna to find and capture the Avatar alive. Upon learning of Korra's apparent demise at the hands of Dark Spirits, he was disappointed with his children's failure but also decided that they could open the Spirit Portal through other means.

Vaatu's Enforcer
It was later revealed that Unalaq is working for Vaatu, who told him that Korra was in fact alive and was coming for him in the Spirit World. Upon Korra's arrival to the Spirit World, Unalaq kidnaps Jinora (who had come with Korra), with a little help from Wan Shi Tong, and threatens to kill her and destroy her soul if she does not open the Spirit Portal for him, forcing Korra to open the portal. He then tries to kill Korra after she opens it but fails.

Shortly after the spirit portals were opened, Unalaq returned to the real world to fight off the remaining Southern Rebels. With the help of the Dark Spirits, Unalaq was able to defeat the Rebels, either by capturing them, or severally injuring them. However, Tonraq showed up in hopes he can defeat his brother. Despite his best efforts, Tonraq was easily outmatched by Unalaq. With the Southern Rebels out of commission, Unalaq focused on having both of his troops and the Dark Spirits guard the Southern Spirit Portal, knowing that Korra would show up to close the portal. Upon having nearly everyone captured, Unalaq reveals his full intention; he wants to merge with Vaatu so he can become a Dark Avatar, just as Wan had done with Raava. Tonraq begs him to reconsider, but to no avail.

Dark Avatar and Demise
Upon Harmonic Convergence, Vaatu was released, and merged with Unalaq to become a Dark Avatar. Upon a destructive battle between the two Avatars, Unalaq/Vaatu proceeded to rip Raava out of Korra, destroying both Raava and Korra's connection to past Avatars. He proceeded to Republic City where he would lay waste in order to bring about a new world order.

While seemingly unstoppable, Korra returned for a second battle with him as a giant spirit (much like Unalaq/Vaatu). During the battle, Jinora's spirit manifested inside Unalaq/Vaatu, creating (and pulling out) a small light that was used to recreate Raava. Raava and Korra then proceeded to use the spirit purification ritual on Unalaq/Vaatu, causing them to vanish.

Although Vaatu will eventually be recreated the same way as Raava, Unalaq is no more.

Korra's Hallucination
Unalaq returned in Book 3: Change as one of Korra's hallucinations. When Korra was poisoned by the red Lotus, Korra hallucinated Ghazan 's head turning into Unalaq's, telling her the time of the avatar is over, and urged her to give up and enter the avatar state.

Powers
Unalaq is a powerful waterbending master, capable of fighting with only a small amout of ambient water at his disposal. His style is varied and aggressive, ranging from water whips, spouts, waves, as well as ice drills and dagger techniques. However, Unalaq's trademark ability lies in his mastery of healing techniques, being one of the few male waterbenders that can use water to heal wounds. Unalaq has adapted this ability into a unique "spiritbending" technique which could calm or provoke spirits. When Unalaq is in the Spirit World, he can use this technique to even corrupt human souls, which results in the death of that human in the process.

As the Dark Avatar, Unalaq's already powerful abilities are magnified, being powerful enough to waterbend the frozen landscape of the South Pole to create ice fissures and enormous waves. Unalaq also gains access to all of Vaatu's spiritual powers, manifesting in his own version of the Avatar State. Unalaq could also transform into an enormous spirit form (a combination of his own body and Vaatu's) that rendered him impervious to most attacks and gave him immense strength.

Trivia

 * Unalaq is similar to Maxim Horvath; they are powerful magicians who serve a more powerful entity (Unalaq: Vaatu, Horvath: Morgana le Fay), yet they're the ones driving the plot.