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The kingdom of Knighton is mine! Tomorrow, the king's castle will be no more and I will rule this land! Until I destroy it, that is..
~ Monstrox declaring his victory at the end of March of the Colossus

Monstrox is the main antagonist of the Nexo Knights series. He is a mighty necromancer, the true identity of the Book of Monsters, Jestro's former sidekick and mentor.

He was voiced by Mark Oliver who also played Lord Garmadon in Ninjago: Masters of Spinjitzu, Mechanikat in Krypto the Superdog, and Lord Licorice in Candy Land: The Great Lollipop Adventure.



Originally, Monstrox was a member of the Wizards' Council. Back when the council was collecting and documenting various types of magic, he studied Forbidden Powers. However, he decided to use the powers for evil and the wizard Merlok had to confront and defeat him, turning his army of Grimrocs into stone in the process. Monstrox was imprisoned, but broke out before he was defeated once again by Merlok and split into twelve books containing his Lava Monsters army which were kept in the wizard's library. In the following years, Monstrox's magic influenced Merlok's sister, Wanda, turning her evil and forcing her brother to petrify her.

Season 1

Monstrox, now stuck in the form of the Book of Monsters, remained trapped in Merlok's library for decades to come, until he finally found a perfect pawn to help him with his plans, that being the royal jester Jestro. After Jestro's performance inadvertently caused a blackout in the capital, the book called him, and introduced himself to the jester. Appealing to Jestro's insecurities, he promised to make him a great villain so that people would stop laughing at him. The two were discovered, however, by Clay and Merlok, and thrown out of the castle by the latter's spell. As the other evil books got scattered across the kingdom in the process, the newly-estabilished villainous duo searched them across Knighton and terrorized its population in the process. While they managed to collect most of the books, Monstrox's plans for conquest were constantly foiled by Nexo Knights.

Season 2

Eventually, Nexo Knights discover the book's true identity, Monstrox. Around the same time he is abandoned by Jestro, however, the jester is eventually captured by the Lava Monsters and brought into Monstrox's castle, who reveals his plan of possessing Jestro's body with the help of the eleven evil books they've collected. When Clay offers the last book in exchange for Jestro's freedom, the book chooses to possess the knight instead. He is ultimately defeated and seemingly destroyed when Clay strikes him with the Techcalibur sword powered by Merlok 2.0's magic.

Season 3

However, Monstrox wasn't truly dead, as his essence took the form of a cloud, named the Cloud of Monstrox. He resurfaces after having been unseen for months, turns Jestro evil once again and goes on to reanimate his Stone Monsters. He and Jestro start searching for the ten Forbidden Powers needed to awaken the Colossus of Ultimate Destruction and use it to not just conquer Knighton, but destroy it. He and Jestro also team up with Roberto Arnoldi, an exiled sculptor holding a grudge against King Halbert. During one of the attacks he zaps Clay with his lightning which makes him slowly turn to stone. After collecting four Forbidden Powers, he attacks Knightonia, blowing up Merlok's library along with some of his memory banks, although Aaron destroys his cloud form, turning him back into a book and forcing the monsters to retreat. Despite this, Monstrox still expresses glee at the chance of him having erased Merlok 2.0 completely.

Season 4

Monstrox regains his cloud form after becoming amused by Jestro getting defeated by children. He reanimates the petrified Clay to force the other Nexo Knights to fight him, knowing that they woulld be unwilling to kill him. This ends up backfiring when Clay turns amnesiac but regains his memories and chooses to battle Monstrox instead, destroying many of his Stone Monsters. Ultimately, the necromancer collects the tenth Forbidden Power, allowing him to awaken and possess the Stone Colossus of Ultimate Destruction and start a kingdom-wide rampage, destroying multiple towns and nearly flattening the capital itself. However, his body is turned crystal and destroyed by Clay and Merlok 2.0's combined efforts, seemingly ending his threat once and for all, until Ruina recovers his crystal heart and leaves without being noticed. Since the show was cancelled prematurely, the story never received a proper conclusion, leaving Monstrox's ultimate fate ambiguous.


In human form, Monstrox wore a purple robe with a cloak and a hood of the same colour, along with a dark blue belt and boots. His face appeared to be completely black with flaming yellow eyes and mouth, although it's unknown whether it was his actual appearance or it was obscured by his hood.

As a book, he has a brown cover, with his pages showing Lava Monsters trapped inside him. His eyes and mouth are somewhat similar to the ones he had as a human.

Monstrox would later become a grey living cloud, nevertheless having the exact same face as before. When enraged, he would gain a darker colour.

The necromancer's final form would be the Colossus of Ultimate Destruction, a stone giant embedded into Mount Thunderstrox possessing two wings, an enourmous jaw, and a cannon in place of its right hand.


Driven by lust for power and vengeance, Monstrox pursues only one goal: the destruction of Knighton. Despite being explicitly ruthless, he surprisingly often comes off as humorous and even affable to others. He can easily manipulate people by addressing their insecurities, which is how he turned Jestro and Roberto Arnoldi to his side. At times it appears that he considers them friends, but at the end of the day, he only uses whoever he's allied with as tools and doesn't hesitate to throw them under the bus if necessary, as proven by his plans to possess Jestro after convincing him that he only wanted to make him a good villain for so long.

At the same time, Monstrox has a horrible victim complex, considering every sign of dissent a personal offense and an act of treason, even if the dissident, in question, suffered from his actions, which potentially makes the necromancer even more dangerous as he will almost certainly try to punish the offender.


More monsters! Make more monsters!
~ Monstrox to Jestro
You gotta learn to be evil,
Don't be a schlimazel!
Learn to be nasty -
Get awful real fasty!
Cause being bad is so neat-o!
Yes, being bad is real mean-o!
~ Monstrox singing in "Kingdom of Heroes"
Jestro: So, you're a cloud?
Monstrox: Oh, I am Monstrox, the arch-necromancer! I can take many forms.
Jestro: Except human, apparently.
~ Jestro and Monstrox
That Mer-loser always thinks he knows the way out. Well, there's no way out this time. Ever since my defeat at the hands of Merlok so many years ago, all I've thought about is revenge. I tried to regain my powers as the Book of Monsters. Then, as the Cloud of Monstrox, I assembled the Forbidden Powers to become the Colossus of Ultimate Destruction. And now... finally... I'll take my vengeance on the kingdom... on the Nexo Knights... on Merlok... on everyone! I'll wipe this realm from the face of the map!
~ Monstrox swearing to destroy Knighton at the start of "The Fall"



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Video Games
Forrest Blackwell | Lord Vortech | Rex Fury | The Rookie

TV Series
Cragger | Crooler | Scorm | Jestro | Monstrox

Other Brands
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Other: Comic Book Guy | Syndrome

See also
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