Brain King is the evil leader of the Brain Factory and was a true mastermind that was behind the creation of the Brains , alien-like parasites that infected various creatures and the Brain Attack on Makuhero City. He was the evil monstrous entity that happened to be defeated by Merrick Fortis and Kirk Thresher 1000 years ago and was sealed away in the hellish planet in the past until he was revived once again to wreck havoc across the entire universe.
Brain King was the evil being that was responsible for creating and developing the Brains. As the result of his ability, he creates the army of monsters by infecting various creatures and thus, mutating them into vicious monsters. Then, he launched the invasion towards the entire universe, believing that his new creations have the rightful place to dwell in the universe. Later during the battle, Heroes Merrick Fortis and Thresher were dispatched and they engaged Brain King in the battle. Eventually, they finally overpowered him and instead of destroying him, they captured him and sealed him away in the distant hellish planet. Upon Brain King's defeat, the invasion was wiped out and the entire universe celebrated their victory of good over evil.
However, Brain King was still confined in the planet but he was yet to be alive. As the result of the event, Brain King immediately began to create the Brains before dispatching them to infect the other beings to add as his army. Soon after that, he launched the attack in Makuhero City . He sends his minions to attack Furno and his friends, though they managed to defeat them with their new forms before begin their mission to save the universe. Brain King eventually created the most powerful monsters before sending them to fight the Heroes. When his work was done, he sent Dragon Bolt, Polyhydrastocyst and Rachnox to fight the Heroes .
Soon after, he devised his ultimate plan that was to destroy Hero Factory and covered the entire universe in hellish darkness. Later when Furno and his friends arrived in his place and confronted him, Brain King immediately assume his true form : his Chimera-like monster form before engaging the Heroes into the final battle.
Brain King's relentless might was proved too much for the Heroes as he easily overpowered them and eventually destroyed their Hero Cores, causing them to lose their powers . It is then Rocka's determination of telling them not to give up as there is still light of hope before transforming into Jet Rocka as the Heroes eventually recovered. Together for the last time, Furno and his friends used their Hero Cores to directly weaken Brain King before Jet Rocka manages to wound him and thus, destroying him.
Brain King was an ultimate, evil entity. He was also completely tyrannical and dictatorial even in the point of destroying his enemies and mutating creatures into the monsters. Based on his ways, he was also much more meaner and brutal as he had no qualms of eradicating everything in his path .
Being a powerful being, Brain King usually appeared in two forms; his astral shadow form and his fully final form . He relies on his brute strength that was powerful enough to take his enemies down . However, he also attacked his enemies with his energy weapons, which he created by using his dark energy . He controls the elements of fire, ice, electricity, earth and darkness.
He was also a creator that he used his knowledge to create the Brains. He also created the powerful version of the Brains by exposing them into energized liquid, thus giving them glowing bodies and some additional powers .
- Brain King was made by combining different sets of Pyrox ,Ogrum, Scarox, Bruizer, Dragon Bolt, Frost Beast and Aquagon.
- He was also the second character to create the Brains, after Witch Doctor who was responsible of creating Quaza Spikes.
- Oddly, his final form is based on the form of Chimera ,a mythical beast of the Greek myth. Due to this, he had different body parts (head of Pyrox, right arm of Bruizer , chest of Frost Beast, left arm of Ogrum, wings of Dragon Bolt , legs of Scarox , and the tail of Aquagon) as they looked like each characters' appearances.