Karzahni is one of the villains in BIONICLE. Although he serves as one of the villains, he eventually became a hidden main antagonist of the 2007 storyline since he was responsible for invading Mahri Nui through of possessing a Barraki called Pridak in search of the Kanohi Ignika, the Mask of Life and conquer the entire Matoran universe and was also the main antagonist in the film-direct-to-video, BIONICLE: The Powers That Be. He was also a brother of Artakha and was a master of Umarak and Devastator.
Due to his powers, Karzahni was also known to be as powerful as Makuta Teridax but whereas Teridax was a being who was pure evil, Karzahni himself was completely an insane entity.
Around 100,000 years ago, Karzahni was created alongside his brother, Artakha by the Great Beings. Soon after their creation, the two beings fought for the Mask of Creation. Karzahni was lost when he was defeated by his brother who claimed the Mask of Creation and he was banished into the island, which he created and named it after his name.
While Artakha chose to make a heavenly island for good Matoran workers, Karzahni chose to take in the bad ones, intending to repair their faults and return them to their homelands. However, his ability to fix the Matoran was not up to par, and he completely rebuilt the Matoran, but into weaker forms. To compensate for his inability to properly repair the Matoran, he gave each of them weapons. He then sent them to the Southern Continent to make sure his failures would not be discovered.
The Turaga eventually noticed that Matoran sent to Karzahni never returned from their exile, and stopped sending their poor workers. Angered by the lack of Matoran coming to him, Karzahni went into denial, blaming the Matoran for his failures. He refused to send any more Matoran away and trapped them within his realm, replacing their masks with his own twisted designs, stripping them of their identities.
Quest in Mahri Nui
It was sometimes during the Great Cataclysm struck the Great Spirit and when Teridax was defeated and Imprisoned by the Toa Metru, Karzahni immediately knows the existance of both Mata Nui and Teridax and he leaves his post in his island in search of power.
At the meantime in elsewhere, the prison called the Pit was heavily damaged and the warlords called the Barraki escape into the ocean, where they transformed into their monstrous forms and at the same time, Karzahni went into the ocean in the search of the Kanohi Ignika. When Pridak was on the verge of death, Karzahni appears and offer Pridak to have a second chance to live in exchange of
The Powers That Be
A few months after the battle in Spherus Magna which resulted Teridax's defeat in the hands of Toa Tahu, the universe was slowly rebuilt from the destruction wrought by Teridax's actions. However, peace was short-lived as Karzahni resurfaced from his hiding and he decided to claim the universe for himself as well as taking revenge on the Toa for his defeat in Mahri Nui. He begins by creating the army of Zyglak and Manutri before commanding them to attack the Matoran Universe. Later he attacked the Toa Inika when they were llooking for supplies in the tunnel in the Archives and brainwashed them. Then, he possesses Velika, a Po-Matoran who was actually a Great Being as well as the member of the Matoran Resistance before he was confronted by Toa Lesovikk and easily defeated the latter and stole his Air Sword. He then traveled to the island of Trem Krom where he extracted the being Trem Krom from his prison before murdering him with Lesovikk's sword in a gruesome way to inspire fear among the population, which he planned