The leader of the Nexo Knights. Righteous and dutiful, he's dedicated to being the best knight he can be. When not in battle, he tends to train to improve his skills even further.
- BFS: His weapon is an incredible huge sword.
- Busman's Holiday: When forcibly sent on vacation by everyone else, the resort Clay's at just happens to be where the Book of Cruelty has wound up.
- The Comically Serious: The steadfast, strict, and dutiful Clay is often put into comical situations due to his teammates' more colorful personalities.
- Farm Boy: In the first episode, he's noted to come from a farm.
- The Leader: Obviously, since he's also the protagonist.
- Punny Name: His name is a pun on his signature weapon, a claymore. It also overlaps with Meaningful Name when you see that in "Knights of the Realm: Part 1", he was given a claymore as a child when he was defending a fellow knight from his cheating sparring partner.
- Why Did It Have to Be Snakes?: He's afraid of failure.
- The Worsening Curse Mark: Suffers this in the third season as his body is slowly being turned into stone. By the end of episode 9, he's turned to stone completely.
The son of a wealthy family, Lance has a tendency to put his needs and wants before his knight's duty due to his upbringing. He doesn't particularly like training or being told what to do, which usually puts him at odds with Clay.
- Animal Motif: Horses. At least twice he's had vehicles that look like or are horses.
- Attention Whore: He loves the spotlight. Conversely, he strongly dislikes it when people aren't paying attention to him.
- Drama Queen: Wails dramatically about how his day is ruined because his phone crashes.
- Headbutting Heroes: With Clay, at first. The two spend all their time bickering about what to do, with Lance disregarding Clay just 'cuz.
- Humiliation Conga: After being an arrogant prat while filming the Golden Castle remake, Lance's armor malfunctions during Jestro's attack, which is all filmed by the director and shown to the entire kingdom at the film's premiere, making everyone laugh at Lance, and causing his agent to dump him in an instant.
- Idiot Hero: He has no idea how to operate his phone, thinking when Ava talks about "back-up" that he needs to literally take a step back.
- It's All About Me: Has the habit of trying to direct all the attention to himself, boasting about his good looks and talents.
- Jerk with a Heart of Gold: As arrogant and condescending as he can be, Lance is steadfastly dedicated to protecting the kingdom.
- Jet Pack: Gains one with his ultra armor form. It doesn't always work.
- Lazy Bum: At first. He even mentions his idea of training is going out clubbing all night.
- Pretty Boy: His looks have earned him lots of adoring fans.
- Punny Name: His name is a pun on his signature weapon, a lance.
- Skewed Priorities:
- When the rest of the team comes down with a serious case of flu, Lance is the only one unafflicted, but is more concerned with whining about his hair.
- When the queen has been kidnapped by Ruina, Lance spends most of the chase bickering with Axl about a game they'd been playing earlier.
- Small Name, Big Ego: When given the part of a lead in a movie, he insists the movie be rewritten to be even more about him than it already was, and starts throwing a tantrum when Clay and Macey dislike the results.
- Spoiled Brat: Big time. Whipperella even states that Lance is a "Spoiled party boy", though he's also willing to protect the kingdom of Knighton, and is a good person most of the time.
- Upper-Class Twit: So very much. A frequent complaint of his is that he won't do something because he has people to do it for him.
- Why Did It Have to Be Snakes?: He's afraid of obscurity.
The thrill seeker who's unable to stay still, Aaron is always ready to participate in anything exciting and dangerous.
- Archer Archetype: He wields a crossbow in battle.
- Full-Frontal Assault: In both "Fright Knight" and "A Little Rusty", Aaron is completely stripped of his armor, leaving him naked in front of everyone to see.
- Good Scars, Evil Scars: Has a notable scar over his right eyebrow.
- Malicious Misnaming: Uses it against Whipperella, which causes her to have a breakdown.
- Mellow Fellow: Is this for the most part.
- Naked People Are Funny: Aaron doesn't mind being losing his armor and walking around naked, and even states that he likes to "Rock the Commando Look" in "Fright Knight" and "A Little Rusty".
- Nothing Is Scarier: His literal fear is doing nothing.
- Punny Name: His name is a pun on arrow.
- Take Up My Sword: Becomes Clay's successor when he turned completely to stone.
- Totally Radical: The poster boy for this trope in the series.
The Knights' only female member, Macy is the daughter of King and Queren Halbert. She much prefers fighting monsters to her duties as a princess.
- Dragon Rider: In season 3, she gets a robotic dragon, which is designed to bond with her as she uses it.
- Expy: She's clearly based on Princess Storm from the 2000 Knights Kingdom 1 theme. With the whole being a princess who wants to be a knight and a father who doesn't really agree or approve of her choices. Heck she's even got red hair like Storm.
- Fanboy: Of the Golden Castle stories. She hates what Lance's ego-trip does to the attempted remake.
- In the Blood: Her mother, the Queen, has a fondness for smashing things with maces as well.
- Kicking Ass in All Her Finery: Despite her hatred of the impractical fancy dress, during series 3 she manages to get into a fight while wearing one.
- Punny Name: Her name is a pun on her signature weapon, a mace.
- Red Is Heroic: Macy's armor is red.
- Talking the Monster to Death: What she technically did to Lavaria.
- Why Did It Have to Be Snakes?: Her worst fear is being a princess, forced to go around in an impractical fancy dress.
- Youthful Freckles: She's got freckles on her face in the television series.
- Animal Motif: Bulls. His armour just happens to look an awful lot like one.
- Berserk Button: He takes his cooking seriously.
- Big Eater: He is as passionate about eating as he is about fighting.
- The Big Guy: The strongman of Nexo Knights. In the sets, it's represented by his having a larger minifigure than the others.
- Genius Bruiser: Despite his brutish, simple-minded appearance, he can be quite clever when he needs to, as seen in "The Maze of Amazement", where he was able to figure which of the maze's walls were fake by strumming his lute and listening for echoes.
- O.O.C. Is Serious Business: As he even notes, when ill he isn't even hungry, and becomes convinced this means he's dying.
- Punny Name: His name is a pun on his signature weapon, an axe.
- Non-Standard Character Design: He is a Top-Heavy Guy, with far more deatailed hands than the other characters.
- Why Did It Have to Be Snakes?: He's afraid of there being no food to eat.
- Animal Motifs: Chickens (or roosters). His insignia is a chicken, and he has been known to use the Rooster's Cry Nexo Power.
- Catchphrase: "None shall pass!"
- Child Prodigy
- Cloud Cuckoolander: Is this compared to Ava.
- Black Knight: His Powered Armor made him this with it's black armor
- Bling of War: His Year 3 sets give him the same golden armor as the main knights.
- Dark Is Not Evil: His Black Knight persona is dark and menicing in appearance, but he uses it to help people and bring fear to the villains.
- Drop the Hammer: His Year 3 sets make hammers his weapon.
- Gadgeteer Genius: He serves as the team's tech department, all on his own.
- Mundane Utility: The Rooster's Cry power just makes the sound of a rooster cawing. Robin uses it to wake up the knights when they're passing out from exhaustion.
- Powered Armor: Used one for awhile.
- Shout-Out: To Monty Python and the Holy Grail. However he's MUCH more braver than his namesake, though he still sports the chicken symbol. There's also the fact that his mech suit is called the Black Knight (And also suffers the same fate as its namesake).
- Child Prodigy
- Deadpan Snarker: Oh so much.
- Gadgeteer Genius: Not as much as Robin, but it's her computer skill that allowed her to unlock Merlok 2.O and send the knights their nexo scans.
- Not So Above It All: Even Ava can't stand Clay's relentless training regime, and joins with the others in shipping him off for a vacation, so she can slack off.
- Punny Name: Ava Prentis is one for apprentice.
- Tsundere: As much as Ava comes across as a grump, she does care about Merlok, yelling she doesn't want to lose him during the series 2 finale.
- Colour Motif: His hologram form is associated with orange.
- Heroic Sacrifice: Sacrifices himself to take out Monstrox for good.
- Last of His Kind: Merlok is the only wizard left in Knighton. And then he goes boom trying to stop Jestro taking the Book of Monsters.
- Mentor Occupational Hazard: Technically, he's already fallen victim to it. It just didn't keep him down.
- Nice Job Breaking It, Hero!: Sacrificing himself not only didn't stop Jestro and the Book, but it also scattered the various evil books around the kingdom.
- Poor Communication Kills: Partly on account of senility. At the beginning of season 2, he tells the knights they need to look for something in the library, but can't remember what. It's only after Jestro and the Book have found it, got it and fled that he remembers what it is.
- Wizard Classic: How he looked in life.
- Bling of War: He's got fancy golden armour.
- Cowardly Lion: He's not much of a fighter. In fact, he's pretty afraid of pain. And anything scary in general.
- Epic Fail: After Jestro takes out all the power in the city, he tries reassuring everyone, and does such a bad job he sends them into a panic.
- Fantasy-Forbidding Parent: He tries to do everything he can to talk Macey out of doing anything dangerous, including not giving her a shield at her graduation ceremony.
- Overprotective Dad: He greatly dislikes the idea of Macey risking her life as a knight, and would rather she simply stay in the castle, where he can keep an eye on her.
- Badass in Distress:
- In her toy forms, in both sets she's been released with, Queen Halbert has or is being imprisoned by the bad guys (and given both times her minifigure comes with a furious expression, indicating she's not taking it lying down).
- She gets abducted by Ruina during series 3.
- Berserk Button: Anything trying to harm her husband and / or daughter.
- Bling of War: Matching her husband's.
- Drop the Hammer: Wields a war-hammer in fights.
- Grievous Harm with a Body: During Jestro's first attack on the city, she fought off some monsters by using one of the guard robots as a club.
- Open-Minded Parent: Unlike her husband, the queen is fine about Macy being a knight.
- Royals Who Actually Do Something: Unlike her husband, the queen is a fighter.
A royal jester with self-esteem issues, Jestro's attempts at entertaining people usually fail miserably, resulting in him becoming the laughingstock of the kingdom.
The Book of Monsters manipulated him to become a villain, and he embraced his new role in hopes of finally being good at something.
- Bad "Bad Acting": He's never been good at acting, even as a child.
- Berserk Button: Being laughed at makes him lose his temper.
- Character Tics: "The Knights of the Realm Part 2" revealed that he juggled as a kid whenever he was nervous.
- Cloudcuckoolander: He insists the earth is donut shaped.
- Evil Costume Switch:
- His jester's outfit turns to red and purple when he touches the Book of Evil.
- Inverted when he turns good, donning an orange and purple outfit with armor on it.
- Evil Feels Good: Enjoys being evil because it's something he's moderately good at.
- Evil Makes You Ugly: He looked like an ordinary person before he touched the Book of Evil. The initial effects include his teeth and eyes turning yellow. As time goes by, Jestro starts looking less and less human at all. Case in point, by the season 3 premiere, his skin now looks like electricity is coursing through it.
- General Failure: His first act on summoning General Magmar, who the Book assures him is a military genius? Put the man to work rigging up booby traps, rather than coming up with a winning strategy.
- Harmless Villain: At first, despite wanting to be evil, Jestro is utterly terrible at it.
- HeelFace Revolving Door: He started out good, but was manipulated by the Book of Monsters into working with him. He reformed in season 2, but was once again corrupted in season 3. After season 4, he manages to side with the Knights.
- Horns of Villainy: Whenever he does something truly evil, his jester hat twist itself to look like a pair of horns. This continue in season 3 where the hat actually emits a torrent of electricity between the two points.
- Horrible Judge of Character: The Book of Monsters easily manipulated him to do his bidding. Jestro later admits that he's never been good at reading people.
- Red Eyes, Take Warning: Well more of a red pupils during season 1 and 2.
- Supernatural Gold Eyes: His eyes glow gold whenever he starts putting effort into being evil.
- Took a Level in Badass: Along with a level in Jerkass, during season 3. He becomes more evil, and more of an actual threat, even talking back to the Cloud on occasion.
- Walking Disaster Area: His attempt at doing a magic show ends with him flinging a power mace into the nearest wiring, cutting off power to the entire city. He also makes a comment in episode 3 that he badly smashed up Ye Olde Royal RV when he performed a show in it.
- Yank the Dog's Chain: Just as Jestro finally gets a chance to be a good comedian, the Book betrays him and preps him for a case of Demonic Possession.
Book of Monsters/Monstrox
A sentient evil spellbook and Jestro's mentor. The Book of Monsters is highly manipulative, requiring an unsuspecting pawn to summon monsters from his pages due to his lack of limbs. He seeks to consume all the eleven books of black magic, which enhance the powers of the monsters summoned through him.
In reality he is Monstrox, the arch necromancer. A century ago Merlok turned him into a book and his evil powers were separated into the eleven spellbooks he seeks.
- The Corrupter: Is responsible for Jestro becoming evil not once, but twice!
- Deadpan Snarker: Often, especially towards Jestro.
- Elemental Powers: As a cloud he can use lightning attacks, and even then it's hinted at with the monsters he created (Lava monsters when he was still a book, followed by turning statues into stone monsters).
- Evil Smells Bad: According to Jestro, he stinks. The Book retorts that he's been sitting on a shelf for a hundred years.
- Fallen Hero: Monstrux used to be one of the Wizard's Council, until the magic he was researching started corrupting him.
- Killed Off for Real: The non-televised ending has Clay utterly destroy him for good.
- Not Quite Dead: First, the Knights destroy his book form, turning him into a cloud. At the end of season 4, he loses the cloud form, but comes back as Monstrux 2.0.
- Red Eyes, Take Warning: His eyes go red with his power up at the end of series 3.
- Sealed Evil in a Can: Technically he is this, way more in season 1 and 2 if you consider his lava monsters trapped inside his pages.
- The Man Behind the Man: Back when he was still the Book of Monsters, he pretended to be a mentor of sorts to Jestro, when in truth he used him to become Monstrux once more.
- Tome of Eldritch Lore: He was a spellbook filled with nasty spells and summonable monsters.
- Villainous BSoD: Finding the Lava Monsters going pacifist sends him into a funk, until it turns out they tricked Jestro.
- Voice of the Legion: During season 3's finale, thanks to the Forbidden Power boost.
Roberto Arnoldi is a sculptor who used to work for King Halbert. One day, he was commissioned to make a "smashing" statue of Queen Halbert. When he literally made a picture of Queen Halbert hammering some Scurriers, King Halbert was displeased, and fired him, despite the Queen actually enjoying it. Upon meeting Jestro and the Cloud of Monstrox, Roberto sided with them in order to get revenge on Knightonia, starting by making monster for Jestro and Monstrox.
- Cloudcuckoolander: Even without his literal-mindedness, Roberto's brain is often somewhere else. When Jestro mentions needing "wheels", Arnoldi starts talking about doing something with wheels of cheese.
- Literal-Minded: Takes what people says literally, for example, when Jestro asks for a rolling headquarters, he literally made a moving base with a noticeable head up front. When asked to make a "smashing" statue of the queen, he made it one of her smashing things.
- Mad Artist: Considering he's aiding Jestro and Monstrox overthrow Knightonia, he qualifies.
- Mook Maker: Has taken this job, as well as creating the new mode of transportation for the bad guys.
- Toyless Toyline Character: He's not present in the toyline.
A group of fire-based creatures who serve Jestro.
- Good Colors, Evil Colors: They favor red, orange, yellow and black.
- HeelFace Turn: They seem to have become good after the events of season 2 and just want to live in peace.
- Mooks: The Ash Attackers, Crush Smashers and Flame Thrower monsters.
- No Body Left Behind: Whenever they're hit with Nexo Power, though that's not much of a problem though as they just return to the Book of Monsters and can be summoned again.
- The Swarm: Seems to be a preferred tactic of magma monsters.
- The Dragon: Used to be Monstrux's right-hand monster. And still is, in fact.
- General Failure: He is apparently the strongest monster the Book ever produced, and is also incredibly clever. That doesn't mean he wins fights very often.
- Samurai Ponytail: Seems to be sporting one.
- Wicked Cultured: Speaks with a refined british accent.
- Beast Master: Able to tame any monster, even the ones conjured up through the Book of Chaos.
- Epic Flail: Wields two of the minion magma monsters as this.
- Eyepatch of Power
- Gadgeteer Genius: He's the one who built the Jestromobile. However, he's not very good at it, since Jestro complains soon afterward. The Book of Monsters explains it's because of the influence of the Book of Chaos - Jestro told him what to do, he just didn't explain very well.
Flama and Moltor
- Bash Brothers
- Fog Feet: Flama has no feet. It's represented in toy form by a version of this.
- Power Fist: Moltor's hands are oversized, presumably to aid with punching folks.
A very talented spymaster, Lavaria is a lava monster who specializes in espionage and thievery. She fulfills her missions without making a single sound.
- Amazonian Beauty: She's got very defined abs.
- Bare Your Midriff: Her top exposes her toned midriff.
- Bat Out of Hell: Her Ultimate form has bat-like wings.
- Femme Fatale: Her introduction is about as close as she can get to being one without destroying the metaphorical radar, even coming complete with Sexophone.
- Ignored Enamoured Underling: She pines for Jestro, but he doesn't return the affection. At least, so the show's website says.
- Master of Disguise: Manages to disguise herself as a robot, with no-one being any the wiser.
- Paper-Thin Disguise: She infiltrates a cooking competition simply by putting on a false mustache. That's it.
- Stealth Expert: One of her skills is sneaking around silently to gather intelligence on the Knights and their allies.
- Yellow Eyes of Sneakiness: Fitting, for a spymaster.
Burnzie & Sparkks
- Cyclops: Sparkks.
- Dumb Muscle: Burnsie is incredibly strong, but very stupid. He's still smarter than Sparkks.
- Starter Villain: The brothers are the first non-Mook monsters Jestro learns to summon, and the first the Knights face.
- Those Two Guys
- Volcanic Veins
- Berserk Button: Aaron appears to be this for her.
- I Know What You Fear: Try to use this against her enemies, but it doesn't work if she can't figure out which thing they're afraid of.
- Reality Warper: Her whips cause their target's worst fears to appear out of nowhere, rather than just making them think they're seeing them.
- Reptiles Are Abhorrent: Unlike fellow female monster Lavaria, Whiperella is much more reptilian in appearance, and not considered as attractive by the story.
- Snake People: The lower half of her body is a snake's tail.
- Whip It Good: Her weapon of choice, as the name suggest.
- Back from the Dead: Unless hit with the Combo-Nexo power, their bodies will just turn back into stone, which Monstrox can quickly fix with his lighting strikes.
- Dumb Muscle: The rank-n-file are good for rushing the enemy, but... well, they've literally got rocks for brains. Even instructions as simple as "stay here" confuse them.
- Evil Counterpart: Some of them have access to the Forbidden Powers, evil versions of the knights' own Nexo Powers.
- Good Colors, Evil Colors: They favor pale blue, gray, purple and a little black.
- Hired Guns: Most were monsters created by Monstrox, but there are some whose origins aren't connected with the archnecromancer.
- Terrible Trio: Most of the high ranking Stone Monsters are usually found in a set of three.
- Theme Naming: Most of their names begin with "r".
- Uniformity Exception: Garg looks like all the other gargoyles, except he's black where they are grey.
- The Corruptible: Due to guarding the forbidden power, each individual Rogul has the ability of the forbidden power they were guarding.
- Fog Feet: With hovering rocks circling them.
A trio of flying Stone Monsters that are good at grabbing.
- Aerith and Bob: Their names are Hilda, Ingrid and Bullwicker.
- Harping on About Harpies
- Taken for Granite: The trio were turned to stone while attempting to nab the Forbidden Power of Ravaging Rot.
As the name suggests they are three evil golem brothers (Roog, Reek and Rumble) who once battled the wizard council in the past. They now serve Monstrox and Jestro in their attempt to rule the kingdom.
- Car Fu: Rumble does this, literally, as his body is now a transport for his two brothers.
- Violent Glaswegian
- Karma Houdini: At the end of season 4, she's still out there. And then the show ended.
- Luke, I Am Your Father: She's Clay's mother.
- Sinister Scythe: A lightning scythe.