In a medieval yet futuristic world, Clay, Aaron, Lance, Princess Macy, and Axl are five young knights who protect the kingdom of Knighton and its capital Knightonia from Jestro.
Knighton is buzzing with festivities on the graduation day of the Knights Academy. In the middle of the party the vengeful jester, Jestro, releases the dangerous Book of Monsters and start making monsters that tear the place apart.
A magic blast from Merlok the wizard saved the day, but now Merlok is gone and Jestro is on the loose with the Book of Monsters.
Merlok 2.0 is glitching and the knights are not able to download their Nexo powers during training. King Halbert allows the Knights to transform his RV into a rolling Fortrex.
The king and queen are giving three people a tour of the kingdom. Meanwhile, Jestro and the Book of Monsters finds the Book of Chaos where Jestro summons up Beast Master to create chaos in one of the realm's city.
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Jestro finds the Book of Fear and feeds it to the Book of Monsters. The jester then brings out spider-globlins and Whiparella, a monster who can find your deepest fears and can bring them to life.
When Lance is cast as the star in the new remake of "Ned Knightly and the Golden Castle", he doesn't anticipate Jestro and his monsters invading the set and ruining his starring role.
The Knights find themselves trapped in a maze looking for the Book of Deception. But will they actually get their hands on it, or will it keep deceiving them?
Leaving the maze with the real Book of Deception, Jestro feeds several books of the same kind to the Book of Monsters to create fake NEXO Knights where Sparkks is given the appearance of Clay.
Jestro and the Book of Monsters travel to the place where the evil wizard Monstrox did his evil deeds and find the Book of Destruction.
Aaron must figure out a plan to save all his friends. When Jestro was doubting his desire to destroy King Halbert, Beast Master feeds the Book of Revenge to the Book of Monsters where it increases the revenge motivation in Jestro and the Lava Monster Army.