|“||I lived ten-thousand lifetimes before the first of your kind crawled out of the mud. It was I who broke through the divide that separated the plane of Spirits from the material world. To hate me is to give me breath. To fight me is to give me strength. Now prepare to face oblivion!||„|
|~ Vaatu to Wan.|
|“||So you've returned, Raava. The Harmonic Convergence is coming soon, and this time, I'm going to wipe you out for good.||„|
|~ Vaatu to Korra|
Vaatu is the overarching antagonist of the entire Avatar: The Last Airbender franchise, serving as the overall main antagonist of The Legend of Korra, specifically being one of the two main antagonists (alongside Unalaq) of Book 2: Spirits.
Vaatu is the evil spirit of chaos and darkness, and the foil to Raava, the spirit of light and peace. Vaatu wants to plunge the world into 10,000 years of darkness and his desire to cause chaos everywhere could potentially result in the world being destroyed. Vaatu's powerful chaotic influence can also corrupt normal spirits and turn them into ferocious, uncontrollable beasts. Vaatu was responsible for the creation of the Avatar cycle, and battled two Avatars; Wan (the first Avatar) and Korra, the last of the old Avatar cycle and the first of the new one.
He was voiced by Jonathan Adams.
Vaatu first appeared engaged in battle with his opposite number, Raava. Attracting the attention of a then wandering Wan, Vaatu convinced Wan that Raava was the instigator of the conflict and was oppressing him. Falling for his ruse, Wan freed Vaatu from Raava's grasp, allowing him to flee. Once freed, Vaatu wasted little time corrupting Spirits and turning them into Dark Spirits, also planning to cause 10,000 years of darkness on Earth.
Wan, realizing his mistake, tried to help Raava defeat Vaatu and the two traveled the world, with Wan learning all four elements so as to better help Raava fight Vaatu. With Raava's help, Wan was able to master them all. Unfortunately during that time, Vaatu had been harnessing the Spirit's anger to become stronger while simultaneously making Raava weaker, also creating more and more Dark Spirits.
Raava explained that in a year, Vaatu would use the Harmonic Convergence to make Raava disappear forever and allow him full power. When the time of Harmonic Convergence came, Wan engaged Vaatu in battle, but Vaatu was far too powerful to be defeated. Raava entered Wan's body and the fight resumed, only for Vaatu to triumph anyway. At that moment the Harmonic Convergence occurred but before Vaatu could complete his plan, Wan used the Harmonic Convergence to merge Raava with his soul forever, making Wan the very first Avatar. Wan was able to then seal Vaatu in a tree and sealed away the Spirit World, putting an end to Vaatu's threat for 10,000 years.
However, as of The Legend of Korra, Vaatu had made efforts to bring to about his return, corrupting Spirits into Dark Spirits and also enlisting the help of Unalaq to free him. Unalaq had convinced Korra to open both the Northern Portal and the Southern Portal, and so upon Harmonic Convergence, Vaatu not only escaped, but also merged with Unalaq to become the first Dark Avatar.
Unalaq/Vaatu proceed to attack the Avatar, rip Raava out of Korra, destroy Raava (temporarily, as one cannot exist without the other) effectively destroying the Avatar cycle, and attack Republic City. When Korra faced them a second time, Jinora's spirit pulled a small light out of Unalaq/Vaatu, recreating Raava. Raava and Korra merge once again, performing the spirit purification ritual in Unalaq/Vaatu, causing them to vanish.
Since one cannot exist without the other, Vaatu will eventually be recreated the same way Raava was, to the next Harmonic Convergence in 10.000 years. His host (Unalaq), however, remains deceased. Additionally, since Unalaq died in the Dark Avatar state, Vatuu will not be reincarnated into a human form.
Vaatu returned in Book 3: Change as one of Korra's hallucinations. When Korra was poisoned by the red Lotus, Korra hallucinated Ming-Hua turning into Vaatu, which later floats up to Korra's face, telling her she is too weak to resist the poison and he is stronger then ever. Emphasizing the futility of her resistance, he urged her to just let go and enter the avatar state.
Vaatu is fairly perfunctory and two-dimensional, as he is consumed by his single-minded and pertinacious objective to destroy Raava and bring about 10,000 years of darkness upon the arrival of Harmonic Convergence. His apparent distaste for Raava is intrinsic to his very nature as her spiritual and extramundane counterpart, though it is further exacerbated when Raava managed to keep him in check and later, after having merged with Wan, sealed him in the Tree of Time, fueling his desire for revenge. Apart from wanting to destroy Raava forever, he follows the similarly narrow path of spreading chaos and destruction, since these are the very things that he personifies and give him strength.
Despite spreading chaos by default, Vaatu exudes an ironic calm, never losing focus of his goal or panicking, even in the face of certain defeat. He patiently bids his time in the Tree of Time for 10,000 years, waiting for someone to free him. He is jaunty, confident, and effervescent in his abilities and his pride waxes to pure arrogance when he deals with humans, a race which he contemptuously disdains, being far older and more powerful than they are, and thinking that no human could ever be a match for him. Even though Avatar Wan defeated him, he refused to acknowledge Wan's reincarnation, Korra, and only refers to Raava when speaking to her. The only human that he seems to acknowledge was his human ally, Unalaq, whom he treats fairly and without contempt, even when Unalaq believed that he had failed Vaatu. This fact further shows that (despite being an innately destructive being) Vaatu is coolly deceptive, fraudulent, calculating, manipulative, temperamental, and unscrupulous, able to put aside his prejudice toward humans to suit his overall goals, even going so far as to merge with one to get even with Raava, turning her own strategy against her. Even in the beginning, while Raava was extremely disdainful and antipathetic of Wan's interference, Vaatu was also extremely appreciative, insightful, and sagacious enough in his desperation to manipulate Wan's love of spirits and trick him into freeing himself from Raava's grasp.
Powers and Abilities
As the spirit of chaos and darkness, Vaatu has the ability to magnify the negative emotions inside other spirits, swaying them to give in to the darker sides of their natures. In turn, he feeds on chaos and anarchy, increasing in both size and power. His airy and transparent body allows him to fly and be unharmed when it is severed by an attack, though it has enough substance to enter physical combat and produce kinetic force. He also has the ability to shoot purple energy blasts from his "face". In his battle with Korra, and later in his assault on Republic City, he also demonstrated the ability to generate vegetation infused with spiritual energy that can take a life of its own by shoving his tentacles into the earth and making vines and other plants grow.
Like his counterpart, Raava, Vaatu is effectively immortal and inextinguishable, having lived for 10,000 years. If he is overcome by Raava, he can gradually reform himself from the vestigial darkness within her. Though they have been separated for 10,000 years, Vaatu still has a connection with Raava, and was able to sense her presence once Korra entered the Spirit World. Vaatu is also fully capable of binding himself with a human being, which was exemplified during the Harmonic Convergence of 171 AG as he merged with Unalaq, thereby producing the Dark Avatar. This merge also allowed Vaatu to gain control of Unalaq's ability to waterbend, though unlike Raava, Vaatu's presence in Unalaq's body manifested itself on the outside, and exhibited more sentience, as both he and Unalaq spoke in unison.
- Raava: His polar opposite who fused with Wan and every Avatar afterwards. Out of revenge, he destroys Raava, ensuring that the Avatar would be too helpless to defeat him. Later, she returns just in time as Korra manages to defeat him.
- Wan: First Avatar to defeat him.
- Korra: Bane of his existence.
- Vaatu's backstory, role, and physical appearance bear some resemblance to Aku, whose voice actor, Mako also voiced another Avatar character, Iroh.
- It is entirely possible that Vaatu was the basis for the Red Lotus. This theory has a fair amount of evidence to it, as the Red Lotus firmly believes that chaos (what Vaatu represents) is the natural order and strives to fufill this wish. Unalaq (a former Red Lotus member) was so obsessed with Vaatu that he actually attempted to fuse with the great spirit. The Red Lotus insignia also strongly resembles the pattern on Vaatu's body, and even has the same black and red color pallette.
- He is voiced by Jonathan Adams, who has voiced several other villains, including Dormammu, who Vaatu is similar to.
- Vaatu is considered one of the (if not the most) biggest threats in the Avatar franchise. As his actions affected both the spirit and physical worlds.
- A recent fan theory suggests that Vaatu used the approaching harmonic convergence to spread dark energy which ultimately caused Fire Lord Sozin to kill his friend Roku and exterminate the Air Nomads. This theory also has some in-universe basis, since, in Beginnings: Part 2, a tribe of firebenders attempted to take lands from spirits for themselves and became violent and destructive in order to achieve this goal. This occurred partly due to Vaatu's malevolent influence growing from the upcoming harmonic convergence. 
- Vaatu and Raava appear respectively to be representations of the yin-yang (Taìjí tú) concept in Chinese philosophy, which is used to describe the way in which opposite forces are interconnected and interdependent in the natural world. In this case, the concept accounts for the duality associated with the fact that Vaatu represents darkness and chaos, while Raava represents light and peace. His attributes, however, are ironically closer in Taoist thought to the ideal of light (yang) than that of darkness (yin); Vaatu is male and aggressive, as opposed to female and calm.
- Furthering the yin-yang comparison, Vaatu and Raava are said to contain vestigial elements of each other within themselves, from which they can regenerate after being defeated. Similarly, each side of the yin-yang symbol bears a small dot of the opposite color, symbolizing how each side bears a part of the other.
- This duality is also apparent in their names and color schemes. In Sanskrit, vatu (वतु) means "silence", which is the opposite of rava (रव), which means "sound". The two spirits are also negative images of each other.
- Vaatu and Raava are also comparable to the Zoroastrian concept of moral dualism, Vaatu being similar to Ahriman/Angra Mainyu in representing darkness and immorality.