"Long ago in a distant land, I, Aku, the shape shifting master of darkness, unleashed an unspeakable evil. But a foolish samurai warrior wielding a magic sword stepped forth to oppose me. Before the final blow was struck, I tore open a portal in time, and flung him into the future where my evil is law. Now the fool seeks to return to the past and undo the future that is Aku."
Though he is capable of shifting form into virtually anything he wishes, his standard form is a roughly humanoid being with a black body, a green mouth, and a red beard extending from the bottom of his chin. He also tends to have six horns, four long and two short, extending from his head, and eyebrows made of red, flickering flame. In his standard form, he also tends not to have legs, with his body simply ending at the bottom with robe-like darkness that sometimes manifests as flames, and he also tends to be several stories tall. A deep droning noise is often heard around him when he appears.
Aku constantly antagonizes Jack, often attacking him when he is weak, and other times defending himself from Jack's own gambits. The two seem doomed never to defeat each other, for though Jack has beaten him on numerous occasions, Aku merely transforms into a creature and escapes, usually calling out a taunt over his shoulder, a fact that he is entirely aware of and even lampshades in "Episode XLVIII: Jack versus Aku".
While he's usually presented as a serious and threatening foe, Aku is also a source of comedy in the show, due to his outrageous design and sometimes wise-guy behavior, supported by Mako's over the top voice-acting.
Only to end in failure. Aku eventually created Ashi, but eventually, he finally met his demise, when Ashi, and Jack returned to the moment when Aku sent him to the future with Ashi, and was finally defeated by him. Never to be seen again.
Aku means "Evil" in Japanese. It is written as "悪" in Kanji. The kanji can also be pronounced as "Waru".
Originating long ago in the depths of space as a formless evil Aku was banished by the three mighty gods Odin, Ra, and Vishnu in order to protect the universe from his influence - yet a small shard of the great shadow managed to survive and flew off into space - for many years this shard continued flying through space until it eventually landed on Earth, causing the extinction of the dinosaurs in the process.
Many years later, the site on which Aku landed would become the ancient island of Japan, which Aku infected like a horrible disease - creating vast forests of evil in the land and threatening to consume it, eventually Aku's threat became so great and impressive that Jack's father decided to rid the land of the demon once and for all using magical-oil made by Buddhist monks, however, when he fired an arrow coated with this oil into the evil entity it didn't destroy it but rather gave it form and sentience, thus forming Aku as a humanoid threat of just unimaginable power.
However, with aid from Odin, Ra, and Vishnu, Jack's father wielded a magical sword powerful enough to defeat Aku and fought the demon, at the end of the conflict Aku was transformed into a tree - yet the imprisonment wouldn't last much more than a decade before a solar eclipse freed Aku again.
Aku would then proceed to lay waste to the kingdom Jack's father ruled and engaged in a battle with Jack himself - Jack very nearly killed Aku for good using the magical sword but Aku threw open a portal in time and transported Jack to a future-world in which Aku ruled supreme.
For the rest of the series, Aku is portrayed as the tyrannical, omnipresent, all-powerful, and manipulative ruler of the world and is an almost unstoppable force - yet he fears Jack, knowing very well that the warrior has the power to slay him, Aku has placed a high bounty on Jack's head and is always trying to dispose of him, whether it be with manipulation, cunning, force, or trickery.
Shadow of Aku
Jack encountered Aku yet again at the Pit of Hate, where Aku uses his fluid to attach to pieces of samurai armor before he can let Jack reach the time portal. Jack battled Aku but was too late to go to the time portal.
Samurai Jack (2017)
Aku returns in the new season and will fight against Jack for the last time, possibly meaning that he will be defeated by Jack and will be destroyed forever. In the series, it is also shown that Aku donated a small portion of himself to the Cult of Aku after seeing the statue they built in his likeness. Afterwards, the cult leader drank the potion which somehow impregnated her, creating the Daughters of Aku.
In the first episode, Jack fights an assassin named Scaramouche the Merciless who claims to be "Aku's favorite assassin". He tries to call Aku that Jack lost his sword, but Jack seemingly destroys him before he can get the chance.
In episode XCIII, Aku wakes up from his long nap and becomes annoyed with his Royal subjects and minions as they come to his lair, bow down to him and give him gifts while he is trying to do his daily routine. When his minions mention that they built more robots to destroy Jack, Aku states that he doesn't care anymore. Aku then creates a clone of himself to serve as a psychiatrist who asks him about what has been troubling him lately. Aku tell the psychiatrist that it has been 50 years since he destroyed all of the time portals and that he hoped that Jack would have just died off the normal way, but, as a result of the time traveling process, not only has Jack not died from old age but he hasn't even aged a single day and has become biologically immortal, deeply frustrating him.
In Episode XCVI, Aku, after being informed by a henchman that the former's lair was under attack by an army lead by the Scotsman, decides to deal with them himself and flew out of his lair. Later, he transforms into a colossal giant ball and effortlessly slaughtered most of the army. After this, he was confronted by the Scotsman, with the latter insulting and ridiculing Aku, stating that Samurai Jack inspired many to oppose him. However, this leads to Aku killing the Scotsman by shooting him with his eye beams. Aku, with a bored tone, only wondered why the Scotsman brought up Jack before returning to his lair. However, unknown to Aku, the Scotsman returns as a ghost and instructs his army (who are all of his daughters as well) to continue to amass their forces and find Samurai Jack.
In Episode XCVII, Scaramouche (now only a head) tries to reach Aku in order to tell him that Jack is missing his sword and calls him from a phone booth on the boat he was riding, although Aku immediately hangs up after Scaramouche is thrown off the boat.
In Episode XCVIII, in a flashback, it is shown that Aku pulled Jack out of a time portal just as he was about to reach the past and then obliterated it, taunting Jack by telling him that said time portal was the last in existence. In his rage, Jack tried to destroy Aku once and for all, although Aku backed out of the fight and transformed the Rams that had been helping Jack into mindless beasts that he soon killed, causing him to accidentally drop his sword into a pit in his horror.
In Episode C, Scaramouche finally reaches Aku's tower and manages to tell Aku about Jack's missing sword, not only causing the demon to snap out of his depression, but also give Scaramouche a new body out of gratitude and both dance in joy. Aku then flies over to Jack's location (in which it is shown that he also killed The Guardian) where he and Scaramouche then laugh at Jack for not having his sword, only to realize that he actually does. Aku then kills Scaramouche by destroying his head and prepares to leave, however, he stops when he realizes that there is a little bit of himself inside Ashi. Aku then has a flashback in which it is shown that he gave some of his essence to the Cult of Aku, and then comes to the conclusion that the High Priestess must have drank the essence and birthed the Daughters of Aku. He then remarks on how she is really a true daughter of his to her and Jack's collected shock and anger. As Jack tries to kill Aku, Aku begins controlling Ashi and forcing her to fight Jack watching from the sidelines as they unwillingly do so while remarking on how his daughter fell for his sworn enemy. Eventually, Aku turns Ashi into a humanoid replica of himself, which Jack cannot bring himself to kill, laying his sword down in defeat. As Ashi is about to lay the final blow, Aku quickly orders for her to stop and grabs Jack's sword. He revels at finally besting Samurai Jack after fifty years.
In Episode CI, Aku broadcasts his victory over Samurai Jack to the entire world. Aku then tells everyone who opposes him that they have no hope as he prepares to kill Jack, however, he soon realizes that he does not know how he wants to kill Jack. After a period of indecision, Aku decides that it is best to let Ashi kill Jack. As Ashi readies to lay the final blow to Jack, almost everyone Jack has encountered ( The Blind Archers, Rothchild and his Canine Companions, The Ravers, The Triseraquins, The Spartans, The "Jump Good" Monkey Man and his tribe and The Woolies) and saved came to his aid and attacked Aku. Aku begins to do a great battle with them while Jack fights the corrupted Ashi who is stopping him from take back his sword, Aku finding amusement in the armies' attempts to save Jack since he is nearly untouchable and cannot be killed by them. Aku splats a great number of Woolies and Blind Archers corrupting them into an army of smaller copies of himself ordering them to attack the rebells. While the rebells are in great difficult against the Aku's army and Jack is unable to take the sword back the Scotsman arrives with his Daughters causing several damages to Aku's army. During the fight Max and the Robots of Andromeda join the army of Jack's friends with their giant robot samurai. At the beginnig Aku mocks the robot only to be brutally beaten up by it and also have his horns teared off, at point Aku starts to get annoyed and furious and decides to change himslef into a rain of spikes to kill all of his enemies. The rain kills many of Jack's friends but is stopped by the powers of the Scotsman. then He checks on his daughter Ashi to see if she has killed Samurai Jack, but thanks to Jack, Ashi frees herself from Aku's corruption and stands up against him. The furious Aku attacks her but is surprised to see that she still has the exact same powers as he does. Without a second to lose, Jack and Ashi summon a portal and send themselves back to the past. The future Aku then looks in sorrow as he realizes that his destruction is imminent.
Back in the past, after Jack's first battle against Aku, the demon has just sent Samurai Jack to the future. After he finishes his speech of meeting him again in the future, he was shocked to see that the future Jack and Ashi have returned on that same spot. As Aku tries to process why he is back so suddenly, Jack immediately charges and begins his short final showdown with Aku. Aku, still greatly weakened by his battle with he previous incarnation of Jack then transforms into a giant rhinoceros beetle-like form to fend him off, but the latter quickly slashes him in two halves with his sword. Jack then completely destroys one, while the other tries to retreat but does not go very far as Jack manages to stab his severed head with his sword and Aku merges into the sword before Jack slams his sword to the ground. At long last, Aku was finally destroyed once and for all as he and his lair begins to explode; avenging all of the deaths and suffering he has committed and ending his tyrannical and magisterial grasp forever. However, Aku's death came at a price as, since he was responsible for her existence, Ashi is erased from time as she was about to marry Jack. Jack then mourns the loss of Ashi, but sees a ladybug as a memory of Ashi and smiles.
Legends of the Multi-Universe (Menslady's story)
He first served Jack of Blades but now serves Galvatron.
The Protectors of the Multi-Universe