I know what you're thinking. That's just armor.
Naju was a Great Being, warrior, mass murderer, and programmer.
Once upon a time, Naju was an ordinary Great Being. He was involved with the Knights of the Great Beings, and was Uterio di Armechio's mentor. However, his mental state became dangerously unstable, and after he murdered a fellow Great Being, he was cast out and somehow stripped of some of his natural powers. He travelled to the Shattered Mirror Universe, where he murdered most of that universe's Great Beings. He also met that universe's Tahar'ok, and the two antagonised each other somehow.
When Tahar'ok crossed over into the OU, Naju followed him. He somehow sealed him and Blackout in another dimension, where they had to cooperate to survive and escape. What this was meant to accomplish, aside from amusement, is unclear.
Later, he hijacked the Enterprise, and dumped the crew into space. He was hoping to reach Atlantis, and despite interference from several of his fellow Great Beings, he succeeded. He proceeded to do nothing there, and returned just in time for the Battle of Mata Nui II. Naju, being his usual crazy self, suddenly decided to join Blackout. He went on a rampage, killing the Sixth and almost killing Lonka. Blackout used the distraction to defeat Tahar'ok, and ordered Naju to dispose of the half-dead Ta'har. Naju then decided he actually didn't like Blackout that much, and instead sacrificed himself to sabotage Blackout's Conduit.
.....Or so everyone thought. In reality, Naju survived, and began travelling between universes, killing most of his counterparts and absorbing their power. As a result, he evolved into a form resembling a hydra big enough to dwarf Great Spirit Robots.
Speaking of Great Spirit Robots, Blackout, Tahar'ok, Zev Raregroove, and Kakamu (SMU) had been given some by the Great Being Merlin, and began using them to fight. Naju chose this moment to make his appearance, forcing them to band together to bring him down. Eventually, they managed to defeat him, and Naju vanished once more.
He reappeared in the midst of the Uterio War, and put an unusually well thought out series of plans into motion. He founded the Brotherhood of Steel and arranged for an artificial intelligence called DAL to be used as the basis for many supercomputers, which allowed him to take control of them at any time. He also built an army of Neo-Ta'har, and attempted to obtain biometal. He was able to activate DAL and the Ta'har army, but his plan was foiled when it turned out that his former protege, Uterio, had found a way to hack DAL, and used it to take control of Side 8. He decided to join forces with Tahar'ok to stop the Moon-Ship. Ultimately, it was User Zev who saved the universe by persuading Feldt Grace, the Breton girl who had been wired into Side 8's systems, to trigger the self-destruct. Naju was severely injured in the explosion that resulted, and was pulled into the orbit of a nearby planet. Shepard, now wheelchair bound, found him, badly burned and mostly destroyed. Contracting Fuk Mi to repair him, they gave him a new body made out of Incultium, and a range of new abilities. He was then launched by JS and Fuk Mi to Tahar'ok, with the last words from JS to him being "'Till all are one".
Soon after he left, a Void ship named Prophecy arrived nearby, and captured Shepard and Fuk Mi in a tractor beam. It gave chase after Strike Naju.
Somehow, Naju and Tahar'ok were merged into Strike Destiny, an entirely new individual with the memories of both of them. He lived on as part of SD, until, perhaps as a result of Naju's instability coming to the forefront, he tried to kill Klak, and was subsequently killed by D-Klak, ending Naju's life for good.