Zen-Aku

Zen-Aku is a Wolf Duke Org who had manifested from the Guardian Merrick Baliton, when the latter needed the former's mask to defeat the original Master Org 3,000 years ago.

Biography
No one knows much of Zen-Aku's origin, only that his Org spirit was locked within an evil Wolf Mask. When Merrick's friend Animus had perished at the hands of the original Master Org, Merrick made the decision that he had to stop their enemy once and for all. Heading into a temple, he'd found the Mask of Zen-Aku, put it on, and used his Predazord to destroy the evil Master once and for all.

However, after Master Org was defeated, the Wolf Mask had seized control of Merrick's mind, turning him into (or merging him with) the evil Zen-Aku. While he still had some of his humanity, he implored his fellow Animarian Guardians to destroy him, but they refused and instead used their Crystal Sabers to seal him away in an underground coffin.

Curse of the Wolf
For 3,000 years, Merrick, now Zen-Aku, remained in stasis until the Master Org of the present-day summoned a General Org named Nayzor, who released the Duke Org on the present-day Guardians of Animaria --- the Wild Force Rangers. Though he had no any memory of his former life, he knew that he wanted revenge on the Guardians who sealed him away 3,000 years ago, and he tried to take it by capturing the Rangers' Wild Zords and turning those he captured against their chosen ones.

Zen-Aku also revealed that his power came from the phases of the moon, as he was at his strongest when it was full. During the New Moon's phase, he was revealed to be human when Cole saw a young man in the river, accompanied by the wolf cub Zen-Aku had rescued.

Zen-Aku was able to control his own Wild Zords, which he called the "Dark Wild Zords", using his flute plate to summon them. He could also combine them to form the Predazord. Zen-Aku's primary weapon was his Crescent Blade, whose blade could open at two notches. While in that position, his weapon's attack was the "Crescent Wave", which was a blade of dark energy that could disable almost any of his opponents.

Meeting Animus
Over time, Zen-Aku's true nature had been revealed, as he began slowly acting more and more human, by starting out with caring for Alyssa, the White Wild Force Ranger and rescuing a wolf cub from an attack from another Org. The Rangers began to grow confused, and even more so, when the spirit of Animus appeared in the sky and urged Zen-Aku to simply "Remember." However, just as his human self (Merrick) was about to break free of Zen-Aku's curse, Nayzor arrived and turned him into his willing slave, making him unable to be reasoned with.

The Ancient Warrior
When Princess Shayla learned that Zen-Aku was really her faithful Guardian Merrick, she tried to piece together the events of the final battle in Animaria. She discovered that the source of the curse put on Merrick was not the Wolf Mask, but his Predazord. After Master Org was defeated, Predazord had turned evil, and its chosen Guardian along with it. She informed the Rangers that defeating Predazord was the only way to break Merrick's "curse". With a new Wild Force Megazord combination, they did so and reverted Merrick to his human form, destroying Zen-Aku's mask in the process.

Unfinished Business
Merrick thought Zen-Aku was gone forever when his Predazord was purified of the evil that poisoned it, but, a few episodes later, Zen-Aku returned with an agenda: to remerge with Merrick and become complete once again. With the return of the Wolf Duke Org, the Rangers began to question Princess Shayla about this event. Princess Shayla explained that when Zen-Aku's spirit merged with Merrick, it was divided among the Mask of Zen-Aku, Merrick, and his Predazord, but with Predazord and Merrick now good again, Zen-Aku (who was now free because the purification of the Predazord broke both curses on the mask, including the one that imprisoned his Org spirit) possessed all the evil power that was once divided, and was now much stronger than he had previously been, proving it by holding his own against the Predazord and the Wild Force Megazord Striker while even being able to block the latter's finishing move. However, after Merrick used a new trick pool shot (taught to him by Willie at the Road House) involving the Predazord's Gator Staff and the Armadillo Zord to break Zen-Aku's horn and weaken him, the Wolf Duke Org was apparently destroyed by Predazord's "Revolver Phantom" attack.

Final Appearance
After Master Org was defeated, Merrick traveled the world, and Zen-Aku returned, offering to join him, since they were both lost souls trying to find themselves.

Powers and abilities
Zen-Aku possesses several abilities like:
 * Crescent Wave: the only special attack of his blade, which was a blade of dark energy that could disable almost any of his opponents.
 * Moon phases empowering: Zen-Aku revealed that his power came from the phases of the moon, as he was at his strongest when it was full. During the New Moon's phase, he was revealed to be human when Cole saw a young man in the river, accompanied by the wolf cub Zen-Aku had rescued.
 * Superhuman strength: he is stronge enough to almost kill the Ranger with almost no effort, using only his blade and his bare hands.Zen-Aku's_speed.jpg
 * Superhuman speed: he can move faster than the Rangers or any other human by the matter, being bearly visible to the human eye only by a purple glow.
 * Superhuman Agility: Zen-Aku's agility, balance, and bodily coordination are enhanced to levels that are beyond the natural physical limits of even the finest human athlete.
 * Superhuman Reflexes: Zen-Aku has demonstrated that his reflexes are heightened in a similar manner and are superior to those of the finest human athlete.
 * Super human resistance: due to his org nature, he is body is much stronger and resiliant to damage than a human body. In the best situation he can be attacked by all the Rangers at once and not getting any damage at all, but even when he is weakened, he is really hard to get hurt (also, his cloth seems to be some sort of armor, this may grant him a better protection from attacks). However, he was seen once bleeding from the right arm, surprising everybody since the Orgs are not suppose to bleed. The reason of it was because, back then he was Merrick with the wolf curse (this could implie that he was half-human). Anyhow, since Merrick and Zen-Aku are no longer the same person he can't blled any more.
 * Superhuman Stamina: Zen-aku's musculature produces considerably less fatigue toxins during physical activity than the musculature of an ordinary human, if is not nothing at all. He can physically exert himself at peak capacity (possibly) for about 12 to 24 hours before fatigue begins to impair him, depending on the moon phase. However, he is capable of increase his stamina to higher levels when there is a full moon.
 * Inmortality: For any effect, he is inmortal, doesn't matter how many times his body is destroyed he always returns with a new body and a new life.
 * Resurrection: he came back from death twice, the first time he did it was a few episodes after his death, Zen-Aku returned with an agenda: to remerge with Merrick and become complete once again. He is later seen after Master Org was defeated, when Merrick traveled the world, and Zen-Aku returned, offering to join him, since they were both lost souls trying to find themselves. The fact that he returned from death twice could implie that he is actually an inmortal.
 * Healing Factor: Although is almost imposible for him to get hurt, he still can be hurt, however he sure heals faster than a normal human being.
 * Knowledge of botanical medicine (apparently): in one episode, he helped the white Ranger to heal her wounds with a botanical medicine he created.
 * Crystal Sabers stealing: he is the only villian with the power to steal the Mega Zords of another Ranger
 * Floating spinning: he was able to spin like a tornado to float in any direction to dodge any attack and attack to his enemies with his sword.
 * Master Martial Artists: he is an expert in the hand to hand combat and in the use of weapons, defeating the Ranger in every fight with ease.
 * Swordsmanship: he was an expert in the use of sword.
 * Super leaping: he can jump very high at really high speed. In almost every fight he is seen jumping from the top of a mountain till the ground where the Rangers are stading in just a matter of seconds, and then returning to the mountain with no effort
 * Zord Summoning (former):  With his flute knife, he can summon his Dark Wild Zords.
 * Size alteration: Like all the monsters in every Power Ranger season, he has the ability to grow up after being defeated.

Crescent Blade
Zen-Aku's primary weapon was his Crescent Blade, whose blade could open at two notches. While in that position, his weapon's attack was the "Crescent Wave", which was a blade of dark energy that could disable almost any of his opponents.

Flute knife
With his flute knife, he can attack to his enemies on a short distance and summoning his Dark Wild Zords. He also plays his flute apparently to relax or for dramatic effect before a fight.

Dark Wild Zords (Former)
Zen-Aku was able to control his own Wild Zords, which he called the "Dark Wild Zords", using his flute knife to summon them.
 * Alligator: the alligator was the whole body of the Predazord
 * Wolf: it was the left arm of the Predazord 
 * Hammerhead Shark: it was the right arm of the Predazord

He was able to combine them to form the Predazord.
 * Black Bear
 * Polar Bear
 * Giraffe
 * Elephant

New Moon
As if it were a real werewolf, he loses all his power during the new moon and return to his human form, Merrick Baliton. However since they are independent entities now, is possible that he doesn't have this weakness anymore.

His Horn
Like all the Duke Orgs, whenever he loses his horn, he loses his power and his life.

Sacred water
Like all the Orgs, he suffers when touching the Sacred water of the temple (though he can survive to this if he cut his horn, but he'll die eventually).

Trivia

 * Zen-Aku name might mean "Meditative Evil" because "zen" in Japanese originates from "Zen Buddhism" while "aku" means "Evil". It might also mean "Total Evil", as "zen" is one possible reading for "all".