|Allies||Demongo, X9, Mad Jack|
|Enemies||Samurai Jack, Scotsman|
|First appearance||Episode I: The Beginning|
|Last appearance||Episode L: Tale of X9|
Aku is the main antagonist in the cartoon Samurai Jack. He is also known as the "Master of Masters", "The Deliverer of Darkness", and the "Shogun of Sorrow". He was voiced by the late Mako Iwamatsu, who also voiced Master Offay from Super Robot Monkey Team Hyperforce Go and General Iroh from the first and second seasons of Avatar: The Last Airbender.
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 bested 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 makes a reference to 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.
The episode The Birth of Evil reveals Aku's origins. Long ago in the vastness of space, a great, formless evil arose. Before it could do harm to the universe, it was set upon by three god-like figures known only as "The Deities". They are Odin, Ra, and Vishnu. During the battle, the deities' attack was fierce and the evil was all but destroyed save for a small fragment that was flung aside and it drifted for an unknown period of time before falling to Earth during the era of the dinosaurs (causing their extinction). It slowly grew and spread like poison over the course of the centuries, creating an ever-spreading forest of black spikes that devoured any who entered. Eventually the forest grew so large that the Samurai Lord of the Land (Jack's father) decided to kill the evil at its source. Armed with a magic oil given to him by Buddhist monks, the Lord and his cavalry rode into the heart of the forest, the Lord himself the only one to survive. Once at the black lake in the forest's center, the Samurai Lord doused an arrow into the oil he was given, shot it into the air, and into the black lake. Instead of destroying the evil, however; the magic arrow gave it humanoid form, sentience, and the ability to shape shift. Thus, the demon wizard Aku was born.
Aku easily defeated the Lord, trapped him on a giant, dead tree, and went on a rampage. The Deities, sensing the good in the Samurai Lord, summoned him to a secret place. Taking the good inside him, they forged an enchanted sword that is capable of harming Aku. Armed with the sword and a magical suit of armor, he plunged into battle against Aku. In the end, the Lord was victorious, but he was unable to destroy him, so he had to settle with trapping him inside the earth in the form of a tree. As he was sealed away, Aku vowed he would one day return. Shortly after, Jack's mother gave birth to him. Determined to learn from this and be prepared in the event Aku's vow came to pass, The Lord and his family decided that they needed a plan.
During a solar eclipse, the tree form that Aku was imprisoned in dissolved and Aku was released. In a castle, Jack was a young child and his father was telling him how he defeated Aku. After the story was done, Jack was left alone, playing with a toy sword. Suddenly, the castle was covered in Aku's shadow. Aku unleashed a vicious attack on the city. Jack's father attempted to get the sword, but Aku captured him before he could reach it. The Lord told his wife it was time to enact the plan they had prepared. Following the plan, Jack's mother escaped with him and the sword. Jack then started on his journey to prepare both physically and mentally for his confrontation against Aku.
Many years have gone since Jack left for his journey. His people, including his father, have become enslaved to dig up the resources of their land so Aku can begin to take over the world. After Jack completed his training, he came back and defeated all of Aku's demonic minions and freed the people of his land.
Jack then went to his tower to battle with Aku. After a vicious battle, Jack eventually overpowered Aku. However, before Jack could finish what his father started, a desperate Aku tore open a portal in time and flung him into the distant future, certain that he will be able to amass enough power to destroy him by then.
Many ages have passed since they last met. During that time, Aku slowly rose to power and enslaved most of the world, plundering its resources. Aku wanted a robot army to help his empire. Aku hired scientists to make the X-Models. All but one got destroyed. The scientists helped Aku make Beetle Drones which are successors to the X-Models so Aku will have power. But he still hungered for more power and opened his ports to the galaxy so he could pillage and dominate other worlds as well. Since then, his slow conquest of the galaxy has drawn aliens to the earth, making it topsy turvy.
Since Jack arrived in the future, Aku has kept a close eye on him and tries to destroy him many times.
Ikra was one of Aku's aliases, just one of several forms which Aku assumed in order to travel closely with Jack. Using his shifting abilities Aku changed himself to the appearance of a young woman with green skin, black hair and a black dress. She/He travelled with Jack across the desert, battling many dangers together. Under the guise of Ikra, Aku and Jack had formed a close bond. Ikra told Jack that her father, like Jack's, had fought with Aku and having lost been forced to spend eternity trapped in a ring of fire and that she was on a quest to find a magical jewel in the desert which was powerful enough to free her father. When Aku reveals himself as having been Ikra the whole time he mocks Jack for having believed the story about her father.
The Hermit was another one of Aku's aliases, just one of several forms which Aku assumed in order to travel closely with Jack. Using his shapeshifting abilities Aku changed himself to the appearance of an old cranky hermit with green skin, white hair and a black robe. He travelled with Jack to find the Gems of Cronus, looking for one gem to the other, in order to resurrect Cronus.
- Shapeshifting: Calling himself the "Shape Shifting Master of Darkness" at the opening of each episode, Aku can change into virtually any form he desires, from a giant dragon to a small insect, or even a beautiful woman. He can also change his size, liquefy himself, stretch, and expand his body. Aku's consciousness can exist even in a part of himself. He typically changes into animal forms that are threatening to fit certain situations, such as a scorpion or an octopus, adapting to the situation. He is however limited to his own colour scheme, no matter what form he takes, it will always be black, red and green. Also, his true reflection will always appear, even in another form.
- Dark Magic: Aku, being a demonic manifestation of a formless evil, is naturally tapped into variuos dark forces. This gives him great magical power and variety likely beyond any mortal dark sorcerer. There appears to be little to no limit to it, as he can perform acts of Necromancy along with manifesting demons, energy projection and various supernatural feats.
- Self Sustenance: Aku needs no food, hydration, or air.
- Interstellar travel: aku is capable of interstellar travel.
- Scrying: Using mystical forces, he can create mid air images to spy upon Jack and other enemies. He seems to need to be aware of their existence before he can track them.
- Superhuman Strength: Aku can manifest considerable physical force when needed, though do to his shape shifting and mystical nature he rarely utilizes simple brute force.
- Time Travel: This was the very ability that Aku had used to send Jack into the future at the beginning of the series, though so far it has only been used once and was a one way portal forward in time.
- Laser Eye Beams: Aku used this ability in numerous battles with Jack and he also used it to destroy the majority of Jack's Kingdom. He can also use this ability to teleport other people.
- Teleportation: Aku uses this quite often to appear before those he has business with, such as the Imakandi.
- Summoning Storms: Aku is capable of conjuring thunder storms through will.
- Object Materialization: The ability to create objects out of thin air. He once used this ability to conjure gold, jewels, and treasure for the Imakandi.
- Telekinesis: Aku has shown the ability to move objects with his mind alone.
- Sonic Scream: Aku was shown capable of producing a powerful scream that causes massive damage to the landscape.
- Necromancy: Aku has been shown in one episode to be capable of animating countless dead bodies, and bending them to his will, for they lack mind and soul.
- Pyrokinesis: Aku can breath streams of fire from his mouth.
- Terrakinesis: Aku has once summoned a natural stone wall, emerging from the ground.
- Immortality: A significant aspect in the series is that Aku is ageless and immortal. Therefore, he needs no food, air, or water and his wounds will merely regenerate nearly all forms of physical injury in moments. He can only be harmed and finally defeated by Jack's samurai sword. It is notable that Aku is also vulnerable to various magical and divine attacks (such as the powers and artifacts of gods). Given his regeneration ability, even the most powerful of divine and mystical weapons have a hard time destroying him.
Known forms he has taken
- Bat: (he uses this form mostly to escape) used lots of times
- Scorpion: used in I and XXX also shown in opening titles
- Gorilla: used in I
- Billy Goat: used in I
- Squid: used in VIII and briefly seen in XXXVIII
- Manta Ray: used in IX
- Spiked Tubeworm : used in IX
- Spider: used in XXXVIII
- Kraken: used in I but also shown in beginning opening titles
- Cobra: used in XII
- Dragon: used in XIII
- Chinese Dragon: used in XXX
- Praying Mantis: used in XXX
- Mouse: used in XXX
- Frog: used in XXXIV
- Fish: used in XXXIV
- Flying Dragon: used in XXXVIII
- Army: used in XXXVIII
- Dark Mass of Shadow tentacles: used in XXX
- Human: used in XLVIII
Despite his nearly omnipotent abilities, Aku has a few weaknesses. These include:
- Color Scheme: Aku's shapeshifting is limited to his color scheme and will remain red, black, and green no matter what form he takes.
- Reflection: Aku's own reflection will reveal his normal form.
- Magic: Though Aku cannot be harmed by normal weapons and attacks, he can only be harmed, defeated and vanquish by Jack's sword and other mystical forces, such as divine weapons and power. Furthermore, the Goddess of Water and her 3 elemental servants are able to harm and defeat Aku with very little effort, although not at the same degree as three 3 gods Odin, Ra and Vishnu. Since Aku was a fragment of the greatest manifestation of evil, he can be destroyed by the strength and purity of a human's (and likely any other living creature) spirit, as stated by Vishnu. This can be seen by Jack's katana, forged from the purity and strength of his father's spirit, are able to inflict an extremely agonizing injury to him, judging by his scream. When possess by Aku, Jack, in his psyche, vanquish and exorcise the demon from him completely by the light of his spirit.
- Illness: In one episode (XLIII), Aku appears to suffer from flu-like symptoms, exposing his lack of immunity to catching diseases.
Aku is evil incarnate, he embodies the very essence of an evil overlord. Cruel and domineering to all he might meet, it's obey or be obliterated with Aku. Arrogant and sadistic by default, he has been the ruler of most of the planet for thousands of years and does not take kindly to disobedience. An example of his cruelty can be shown when an alien prince and princess had crash landed on the earth and begged him to help them because they needed to get back to their planet to stop an invasion; Aku had them thrown in prison to be tortured in order to "add to their misery".. The same episode also showed a dog in his castle being tormented by electrocution and whipping for unknown reasons. Although he is merciless and inhumane, to say the least, he has enough of an understanding of humanity to successfully manipulate and control people when his powers aren't enough.
Despite this, he possesses a dry sense of humor and often jokes when in a good mood, frequently mocking Jack whenever he can and whatever he can. For instance, in one episode Aku holds a time portal just out of Jack's reach as Jack jumps for it.
He also provides humor to some episodes in more indirect, physical ways. For example:
- In one episode, Aku steals Jack's sword and ultimately strikes at him while Jack is utterly defenseless and immobile. At this point, Aku is as excited about his victory as a child in a candy store. Rather than piercing Jack's chest, the sword simply bounces off his skin with a metallic cling, leaving both opponents speechless. As soon as Aku sees this, his face is shown in close-up. He does not move, his pupils shrink and his flaming eye-brows extinguish with a sound like that of a loud bunzen burner being turned off abruptly.
- In the same episode, before Jack arrives at the location where they would fight, Aku was spying on Jack to loudly loathe his existence and await new oppurtunities for an attack. When Jack arrives at a junction in the road, he decides to leave his choice to fate. He picks up a stick and tries to "sense" the best destination by pointing it both ways. Following that, he throws the stick into the air and follows the path it points at after landing. During this entire scene, which lasts quite long, Aku is repeatedly shown as he spies on Jack. Each time, Aku has a plain expression and clearly has no clue whatsoever as to Jack's intentions with the stick. He doesn't move or even blink, he just sits perfectly still and continues to look dumbfounded until he finally realizes what Jack is about to do and sabotages the stick's landing direction.
- In another episode, Jack finds an ancient, inhabited, secret temple. Upon meeting the temple's grand master, Jack remembers Aku's ability to spy on him wherever he goes and loudly tells his host that he must leave immediately. The grand master then tells Jack he's blocking Aku's vision using what he describes as a large shield. The next scene shows large creatures equipped with searchlights scouring the jungle (resembling search helicopters), followed by Aku glaring at and banging on his spying screen, which is showing white noise like a TV and clearly sounds like glass when he hits it. Combined with the knowledge that Aku has a rather comfortable chair to sit in while spying, one can almost visualize him reaching for the remote control and changing the channel.
Aku is wise as he is powerful, and his sadistic cunning knows little end, from taking the form of a woman to trick Jack or manipulating various races into serving him. He has no remorse whatsoever about telling someone he will save their village if they obey his command, only to then destroy said village as soon as the command is carried out.