Gengo

was the leader of the Enlightened Ones and a despot of the Land of Silence, until his capture and imprisonment by Konohagakure Anbu.

Background
Gengo, alongside other fellow shinobi from Kirigakure at the time, allied with Zabuza Momochi in rebellion against the Fourth Mizukage: Yagura Karatachi, and his destructive methods of ruling over the village. Due to a traitor in their group, however, Zabuza and the rest of his followers, including Gengo, were forced to flee the village forever. After the incident, Zabuza and most of his other followers began collecting capital as mercenaries, never letting go of their dream to go back to their motherland. When Zabuza began accepting work from corrupt people, however, Gengo — alongside many others — left and became disillusioned about such goals.

Upon leaving the group, Gengo made his way to the Land of Silence and took over the nation. During his time ruling it, he developed a speech-induced genjutsu to further his goal of controlling others to do his bidding.

During the Fourth Shinobi World War, Gengo grabbed the opportunity to put his new abilities and plan into action, abducting young men from war and placing them under his control to form the "Enlightened Ones". This continued for two years after the war and he slowly built up his power, having brainwashed minions to take smaller missions from the Shinobi Union in hopes of building a vast amount of capital for his goals. His followers had even gone beyond the Land of Silence and infiltrate each of the Five Great Shinobi Countries without raising suspicion; willing to stir an incident among their citizens at Gengo's command and putting the Shinobi Union in jeopardy of terrorism.

Personality
Gengo is a man of ideals, much like other potential revolutionaries who have come before him. Like Obito Uchiha and Madara Uchiha before, Gengo sees the world as something that must be changed; however, his stance is largely different. Gengo believes that the shinobi, due to possessing immense powers through their ability to mould chakra into various forms of jutsu, should be the ruling class of society. With his ambitions, he planned to unify the continent and have shinobi take over, taking the land from the rule of the daimyō and ending what he called the persecution of the shinobi.

Due to the confidence he placed in the rightness of his ideals, and the effectiveness of his auditory genjutsu, Gengo was seen as a man of charisma; he possesses a silver tongue and can assemble people through words alone. However, due to this, as Shikamaru noted, he is very arrogant. Furthermore, he's not above using methods of torture to get people to bend to his whims, as seen with Rō and Hinoko. Regardless, he has a sense of formality, treating people he intends to place in high positions, such as Shikamaru Nara, considerably better while they are prisoners. Despite this, he devolves into a rage when he finds someone who cannot be controlled and was more than willing to kill Shikamaru when the latter was freed from his genjutsu and refused to fall under its effects later on.

Genjutsu
Gengo is a very powerful genjutsu user, having the ability to create mind-controlling illusions, which are nearly undetectable and impossible to block or dispel, even when figured out by the victim. He himself has mastered Demonic Illusion: Cajolery of Glamour, a voice-induced genjutsu of his creation which allowed him to control targets using only speech; leaving them in a brainwashed state and making them worship him. He also employed the use of a special flower found within the Land of Silence that stirs up specific memories for people inhaling its pollen, which made his genjutsu more effective for reconditioning as a result. After losing his ability to speak, however, Gengo became incapable of using such genjutsu again.

Kenjutsu
Growing up in Kirigakure and being a follower of Zabuza — himself a member of the Seven Ninja Swordsmen of the Mist — Gengo is trained in kenjutsu. In the anime, he is shown able to summon a massive broadsword not unlike Kubikiribōchō. Though his skills are not entirely known, he was able to strike down a number of Shikamaru's clones before being subdued by the Konoha-nin.

Shikamaru Hiden: A Cloud Drifting in Silent Darkness
As Gengo's Enlightened Ones began to grow, he began to attract attention to himself from the rest of the world, particularly the Shinobi Union as they began to realise many of their young men began to disappear while investigating his nation for stealing their potential jobs. His latest brainwashed recruits, which included rising star in Konoha's Anbu Sai, prompted Konoha to order his capture or assassination.

During one of Gengo's many speeches meant to keep everyone in Curtain Village, Gengo captured Konoha shinobi meant to assassinate him — Rō, Soku, and Shikamaru Nara, who (while under the effect of his genjutsu) he had quickly detained. Upon realising he had captured Shikamaru, Gengo was ecstatic and quickly started attempting to sway the young genius into becoming his right-hand man. Despite almost succeeding in placing Shikamaru in the brainwashing genjutsu, Temari and a battalion of Suna and Konoha shinobi stormed Gengo's throne room and interrupted Gengo's genjutsu. Much to his horror, Shikamaru quickly was able to understand Gengo's abilities and Temari began using her Giant Folding Fan to create a vacuum to drown out Gengo's chakra infused voice.

Realising he had been defeated, Gengo fled his Enlightened Ones as Shikamaru gave chase. In a darkened room, Gengo tried to use kenjutsu to kill Shikamaru but due to Shikamaru's master plan and the arrival of Shikamaru's Anbu partners and the rest of Team Asuma, Gengo was detained. Hinoko then used her Chakra Needle to disable Gengo's ability to speak ever again, demoralising Gengo as he was taken away to the Shinobi Union's headquarters in the Land of Iron.

Legacy
In the anime, a decade after Gengo's fall from power, the Land of Silence became a lawless country where criminals festered about.

Trivia

 * means "language", which may come from his technique.

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