The forces of Kronos of the Percy Jackson and the Olympians series. For the full list of characters, click here.
Played by: Robert Knepper
The King of the Titans and suitably the most powerful. He has domain over time and harvest.
- Abusive Parents: He literally ate his children as soon as they were born because it was foretold that he was destined to be overcome by his own sons.
- And I Must Scream: He literally cannot die. The first time, he was chopped into bits and pitched into Tartarus. The second time, his consciousness exploded and was spread so thinly across the world that there's little hope of it reassembling.
- Archnemesis Dad: To many of the Olympians.
- Asskicking Equals Authority: Became King of the Titans through being the most powerful, being the one who killed his father in the original mythology.
- Batman Gambit: Allowing the Fleece to be returned to Camp Half-Blood so Thalia could be brought back to life, and he could count on her Fatal Flaw to sway her to his side so he could have a chance to control the Great Prophecy. It fails.
- Big Bad: Of the Percy Jackson and the Olympians series. His goal is to be resurrected, and the demigods and gods have to stop him because it would mean the fall of civilization.
- Big "NO!": Lets one lose when he's finally defeated.
- The Chessmaster: Manipulates people and events to further his goal of reforming and taking over the world.
- Complete Immortality: Like most divine beings in the series, Kronos simply cannot die. Period. Not even cutting him into numerous pieces will truly do the trick. That said, after his essence gets scattered across the world, other characters theorize that he might never regain consciousness, let alone physcial body.
- Composite Character: The book series makes the common mistake of morphing the Titan Cronus with the primordial god of time, Chronos. In the myths, they were two separate beings who did not share the same powers.
This is at least forgivable, since there is evidence that the Cronus and Chronos were often conflated even by the ancient Greeks.
- Demonic Possession: Because Kronos never fully recovers from being mutilated, he can come into being only by possessing someone.
- Karmic Death: The first time around. Given that this mythology version where Kronos chopped Ouranos into pieces rather than merely castrating him, Kronos suffers the exact same fate done with the exact same weapon he used.
- Eldritch Abomination: Described as such.
- Jumped at the Call: Percy Jackson's Greek Gods says he was eager indeed when Gaea asked the Titans who will kill Ouranos.
- Lean and Mean: His original body is described as being far less impressive physically than his fellow Titans, but even back then he had an evil gleam in his eyes and was the only Titan who willing stepped up to the task of killing Ouranos.
- Overarching Villain: He is the ultimate Big Bad of the series who is the king of the Titans, a being who wants to destroy Olympus and start a new age of Darkness. Even the first three Big bads were merely his servants.
- Sadistic Choice: In the fifth book, Kronos frequently threatens to kill Percy's friends unless he surrenders to him.
- Sealed Evil in a Can: Initially, his remains are just in a particularly creepy sarcophagus that gets stronger every time a demigod forsakes the Olympians and joins his side. Later, Luke graduates to being his Soul Jar.
- Sinister Scythe: His Weapon of Choice.
- Time Master: Kronos seems particularly fond of slowing time around his opponents to a near stop. Percy Jackson's Greek Gods has Percy state that back when he was king of the titans, he liked to use his powers to speed up time for his victims, causing them to crumble to dust due to aging. (Notably, his powers do not, in fact, include Time Travel, despite being the Titan (and thus personification) of Time.)
- We Can Rule Together: Offers this a bunch of times. Most of them are insincere.
- Xanatos Gambit: a big one in the second book. He gets Luke to poison Thalia's tree, which protects Camp Half-Blood and can only be cured by the Golden Fleece. There are three possible outcomes for this plan, and all of them help Kronos in some way:
- The heroes fail to find the Fleece. Then the barrier is gone and Kronos' forces are free to raid Camp Half-Blood, killing many of his enemies.
- The heroes find the Fleece and then Luke steals it. Then he can use it to bring back Kronos, allowing him to destroy the Olympus and Western civilization.
- The heroes find the Fleece and Luke fails to steal it, so they bring it to Camp Half-Blood and cure the tree. Then they also accidentally resurrect Thalia, daughter of Zeus and another possible subject of the prophecy and so a possible pawn for Kronos other than Percy, making Kronos' win more likely.
- Yellow Eyes of Sneakiness: All the more identifiable considering that he possesses people to function. When he possesses Luke, for example, the latter's eyes turn from blue to gold.
- You Have Failed Me: Kronos decides to let Atlas rot due to his repeated failures.
Demigods
Played by: Jake Abel, Samuel Braun (young)

Son of Hermes and May Castellan. When he was an infant, his mother tried to become the new host for the Oracle of Delphi. It went horribly wrong. May went crazy from visions of her son's eventual future and became The Ophelia, and spent Luke's childhood babbling at him about his horrible fate. He ran away and met up with Thalia and Annabeth; they eventually made it to Camp Half-Blood, but not before Thalia died. Luke went on a failed quest and came back with a scar. He is a major villain in the first series, second only to Kronos, attempting to destroy the gods for their manipulation and abuse towards him.
- The Ace: Good looking, charismatic, a good fighter, and his cabin's counselor.
- Broken Ace: And by the time we meet him, he's jaded, unhappy, and desperately craves affection from his aloof father.
- Always Someone Better: To Percy.
- Anti-Villain: Gradually revealed to be this as the series goes on and his more redeeming qualities and tragic backstory come to the surface.
- Broken Bird: Rare Male Example. His hatred of the gods stems from his own bitterness after being basically abandoned by his father his entire life.
- Belated Backstory: Until the fifth book, all we know is that his dad sent him on the quest where he got his scar, and he hates him for it.
- Big Bad: He's effectively this for the first two books, as Kronos is at that point Sealed Evil in a Can and none of the higher-ranking Titans show up until the third.
- Big Brother Mentor: To Percy in book one. Implied to have been one to Annabeth too.
- Big Man on Campus: Seemed to be this before betraying the camp — he was counselor of the Hermes cabin, attractive, relatively popular, and a Big Brother Mentor to Percy.
- Calling the Old Man Out: He's pretty pissed at Hermes, not gonna lie.
- The Chosen One: He is "the hero" described in the Great Prophecy, not Percy.
- Chronic Backstabbing Disorder: No matter how he claims otherwise, he keeps hurting Annabeth, the only camper he has protected up until his FaceHeel Turn. Including the time where he poisoned Thalia's tree, tricked Annabeth into taking the sky, and literally wounded her at the end of book five. He doesn't realize it until the last part.
- Cool Sword: Backbiter. Doubly deadly due its being fashioned out of both celestial bronze and steel, meaning it can kill both mortals and gods.
- Crying Wolf: Before Kronos possessed him, he ran to Annabeth, begging her to run away with him. This was after he tricked her into taking the sky and then took her hostage. She obviously turned him down and it was probably the right decision at the time, because the boy cannot be trusted.
- Dark Messiah: Definitely twisted and evil as well as basically Kronos's champion, but eventually saves the world.
- Driven to Suicide: For a good cause. See Heroic Sacrifice below.
- Driven to Villainy: His bitterness at his father and the treatment of those in the Hermes cabin drive him to betray the camp.
- Demonic Possession: Reluctantly allows Kronos to possess him as the last resort for Kronos's resurrection.
- The Dragon: Kronos' right-hand demigod and primary agent. He also serves this role to Atlas during The Titan's Curse.
- Dying as Yourself: As Luke, not Kronos.
- FaceHeel Turn: Goes from friendly, if somewhat aloof, mentor character to Percy to one of the major antagonists in the series. And back again, if only for a few moments.
- Fallen Hero: After joining Kronos.
- Forgiven, but Not Forgotten: How the demigods treat Luke after his death, along with any other counselor that turned traitor. While Percy acknowledges he died a hero's death and made the right choice in the end, everyone acknowledges that Luke also made bad choices and hurt the ones who cared about him.
- For Want of a Nail: He and Percy are this to each other. They're both sweet, compassionate fighters who become highly admired by their colleagues. Both are proficient swordsmen, handsome, and both consider Annabeth to be one of the most important people in their lives. They even have similar narrative voices, as demonstrated by his first-person short story in The Demigod Diaries. The divergence hits with their mothers. Luke's mother was tragically driven insane when she attempted to channel the spirit of the Oracle of Delphi and spent most of his childhood babbling at him about his awful fate, leaving him scared, resentful, and starved for affection. His anger towards the gods was only increased by a quest that left him scarred and mostly ignored by the gods, including his father. He lashes out towards the manipulation by trying to unseat them and almost brings about the end of the world. By contrast, Percy is closer to his mother than anyone, and it's heavily implied she taught him everything he knows about kindness, morality, and love.
- Freudian Excuse: Once you find out his backstory in The Last Olympian. His mother's kind of crazy and his father's distant, driving him to run away.
- Good Scars, Evil Scars: He has a scar on the right side on his face and as the series progresses, it becomes more prominent. Percy states it looks fresh by the last book, though it's never explained why.
- The Heavy: For the first four books in the series until Kronos breaks free from his can and takes possession of Luke's body.
- He Who Fights Monsters: Started out on the good guys' side, but eventually his resentment against the Olympians drove him to Kronos's side. Percy eventually calls him out for how he may be right about how the gods treat their children, but Luke is only making their situation worse.
- Heroic Sacrifice: Stabs himself in the side to save Olympus.
- Heroic Willpower: Throws off Kronos' possession long enough to apologize to Annabeth and complete the above sacrifice.
- Honey Trap: For Silena; he seduced her and set her up as The Mole, a decision she later comes to regret.
- Hypocrite: Accuses the Olympians for their horrendous crimes, yet he sides with the Titans who are no different. Percy calls him out for hurting the campers as badly as the gods hurt or ignored them.
- I Cannot Self-Terminate: A special case, in that he can self terminate, he just needs Percy to give him a knife.
- Icy Blue Eyes: Percy describes them as "piercing."
- "I Know You Are in There Somewhere" Fight: With Annabeth during The Last Olympian.
- Karmic Death: He chooses it, however; Luke is fighting an injured Percy and Annabeth in the climax, while Kronos is possessing him. As Annabeth falls, she reverts to her previous childish demeanor and reminded Luke he promised to never hurt her. Luke pauses, stunned, and gets a Heel Realization. He then stabs himself with Percy's knife, in his weak spot, before Kronos can stop him. As he's dying, Luke promises Annebth that he'll reincarnate and try to be a better person.
- Kick the Dog:
- He framed Percy for stealing the lightning bolt and Hades's helm, even though Percy at the time was an Innocent Bystander and an Unwitting Pawn. Then he tried to kill Percy after the latter survived.
- Tricking Annabeth into taking the sky and then using her as a hostage was not one of his finest moments.
- Like Brother and Sister: With Annabeth, and Thalia to a degree. They're a little family for sure, but sometimes he and Thalia come off more as parent substitutes to their little girl. The fact that Luke forgets this and has hurt Annabeth multiple times, to the point where she gives up on him at two different points in The Last Olympian, is an important plot point.
- Living Bodysuit: To Kronos after the latter possesses him.
- Love Redeems: In the end, his love for Annabeth drove him to perform his Heroic Sacrifice.
- Luckily, My Shield Will Protect Me: Luke having a shield to defend himself with is a major factor in his victory against Percy in ''The Sea of Monsters".
- Meaningful Name: A castellan is the noble tasked with defending a castle. So who's the one who ultimately protects Olympus? And as noted on the main page, his name means "light" or "light-bringer". Which sounds pretty nice until you realize it means that because it's derived from Lucifer.
- Moral Myopia: He is angry about how the gods ignore their children and let them suffer. Then he starts causing some of the suffering, using campers as pawns the ways the gods do, and Luke justifies it. It's not the first or second time of nearly killing Annabeth, tricking her into "saving" him or using her as a hostage that made him realize he was too far gone. No, it was when he injured her while Kronos was possessing him that spurred his Heel Realization.
- My God, What Have I Done?: In The Last Olympian, when he realizes he's hurt Annabeth again and broken his promise to her. It's the last straw in a larger revelation about exactly how much damage his spitefulness has caused.
- Overarching Villain: He has appeared in most Percy Jackson titles, being the Big Bad of the first two books and he is also the The Dragon to Kronos, the true Big Bad of the series.
- Oxymoronic Being: His sword Backbiter, a specially made half-steel, half-celestial bronze blade that can kill both mortals and monsters. Percy describes it fighting against itself, like two opposing magnets stuck together. It's actually the "beta" form of Kronos' scythe, and has to be bathed in blood in order to fuse the metals together.
- Promotion to Parent: For Annabeth when they were on the run.
- Rage Against the Heavens: He wants to resurrect Kronos in order to destroy the gods.
- Redemption Equals Death: Kills himself in order to defeat Kronos, who his body has been jacked by, and save the world.
- Ship Tease: With Thalia in The Titan's Curse and The Diary of Luke Castellan.
- Soul Jar: For Kronos.
- Supernatural Gold Eyes: When possessed by Kronos.
- Tragic Hero: He Used to Be a Sweet Kid, but his bitterness from being abandoned by his father Hermes drove him to betray his friends at Camp Half-Blood and plan to destroy the gods.
- Used to Be a Sweet Kid : Evident in his diary.
He sounds a lot like Percy.
- The Vamp: Rare Male Example. Silena's confession in Olympian features Rick trying as hard as he can to play this trope without his editors coming down on him. She's the only person who explicitly accuses him of it, but given his penchant for straightforward manipulation, it's not out of the question that it was a regular strategy for him.
- Villain Has a Point: Luke despises the Olympians for being a bunch of psychopaths who use their children as slaves. He believes that they must be exterminated.
- "Well Done, Son!" Guy: "You said they cared about me!"
- Well-Intentioned Extremist: At the end of the day, his main motivation is a desire for the half-blood population to be acknowledged by their parents, instead of used as pawns and then pushed aside. Problem is, he thought resurrecting an Obviously Evil primordial entity was a valid social justice movement.
- We Used to Be Friends: He was popular and well-liked in the camp before his turn to evil, and this dynamic is especially pronounced in his interactions with Thalia and Annabeth (with whom he shares history) and Percy (who saw him as a Big Brother Mentor).
- Willing Channeler: Kronos coerces him into submitting to possession.
- Woobie, Destroyer of Worlds: To the point when even the victims of his nefarious acts (Silena, Thalia, Annabeth) show compassion for him and want to help him. Even Percy, who out right resents him feels bad for the guy in the end.
- Worthy Opponent : To Percy
Played by: Danny Le Boyer

Son of Nemesis, the goddess of revenge and balance, Ethan was one of the many residents of Cabin Eleven who went unclaimed or had no cabin of their own because their parents were minor gods. He promised his mother he would make a place on Olympus for the minor gods, and in exchange she took his eye.
- Anti-Villain: He doesn't desire anything for himself. Instead, he wants to elevate his mother and other minor gods to be on the same level as the Olympians, after being sick of seeing them getting sidelined all the time and receiving no respect from everyone. This is a very, very honorable goal, yet the heroes (including Percy), who are mostly children of the Olympians, are very slow to empathize or catch this up. The only thing that stops him from becoming a
Designated Villain is that the side he currently works for, the Titans, are Always Chaotic Evil.
- Eyepatch of Power: Wears one to cover his missing eye.
- Eye Scream: His mother took his eye part of the promise that he would change Olympus for the better.
- Fallen Hero: As a former camper.
- Famous Last Words: "Deserve better... if only they just... had thrones..."
- HeelFace Revolving Door: Starts out as a hero, then turns to Kronos's side, then turns back to being a hero again at the last second in The Last Olympian, resulting in his death.
- Hoist by His Own Petard: When he tries to kill Kronos, Ethan's blade shatters and one of the pieces spears him.
- I Just Want to Be Special: He turned against the gods and joined Kronos because he was tired of being considered a nobody at Camp Half-Blood for being the son of a minor goddess.Ethan: All I want is respect, Jackson. The gods never gave me that. You wanted me to go to your stupid camp, spend my time crammed into the Hermes cabin because I'm not important? Not even recognized?
- Master Swordsman: While he eventually loses, he fights evenly with Percy in The Battle of the Labyrinth and duels Annabeth in The Last Olympian.
- Mook Lieutenant: Kronos/Luke's main demigod subordinate during The Last Olympian.
- Pride Before a Fall: His mother is the goddess that causes the "fall" part of this trope. Ethan himself follows in her footsteps.
- Redemption Equals Death: In The Last Olympian, he changes sides at the last second when he realizes that Kronos doesn't build, only destroys, and tries to kill Kronos. Kronos, in turn, kills him for turning against him.
- Scales of Justice: Ethan Nakamura's burial shroud has a set of scales on it. This is because Nemesis is his mother.
- Small Role, Big Impact: While there are several other factors, Ethan's desperate goal to elevate his mother is basically what pushed Percy to campaign for the rights of the minor gods at the end of the The Last Olympian, something that is duly granted, thus granting 10 and more cabins to be constructed in Camp Half-Blood for The Heroes of Olympus series and beyond.
- Stealth Pun: He is blind in one eye. His goal is to bring justice for the minor gods. You could say... justice is blind. (Or, in this case, half blind.)
- Tarot Motifs: 8th/11th, Justice. The card shows a blindfolded woman holding a sword and scales. Ethan has one eye missing and his burial shroud is embroidered with crossed swords and a set of scales.
- Ungrateful Bastard: Despite Percy saving his life, Ethan pledges his loyalty to Kronos. This is the last demigod needed to resurrect Kronos.
- Anti-Villain: In the first series, he was one of the demigods working for Kronos.
- Armor-Piercing Question: After Claymore asks what happens when we die, Alabaster asks him why after all his research he doesn't know.
- BFS: According to Claymore, his sword must weigh a hundred pounds.
- Cain and Abel: The Abel to Lamia's Cain.
- HeelFace Turn: In his debut story at least, he works with Claymore to defend against his murderous sister Lamia. Alabaster acknowledges that he made a bad choice in supporting Kronos's forces, and is working to make up for that.
- Human Mom, Non-Human Dad: Presumably inverted, since he's a demigod and his mother is the goddess of magic.
- Welcome Back, Traitor: Averted, as he can't go back to Camp Half-Blood.
Titans
- And I Must Scream: Has been holding up the sky for a very, very long time.
- Archnemesis Dad: To Zoë.
- Arc Villain: Of The Titan's Curse.
- Blade on a Stick: Uses a spear during his fight with Percy, Artemis, and Zoe.
- The Brute: Is the most physically strong of the Titans.
- Evil Sounds Deep: His voice is described as being very, very deep.
- Genius Bruiser: Despite being the Brute, he also is shown to be quite intelligent and a fairly good manipulator.
- Humans Are the Real Monsters: The reason he likes to recruit Muggles; he feels like they are easy to corrupt, and as such make for good minions.
- Knight of Cerebus: The fight with him is the first one in the series where a questmate dies.
- Large and in Charge: The General of Kronos' troops, and described as incredibly tall and large.
- Offing the Offspring: Does this to Zoë.
- Sealed Evil in a Can: The sky itself is a fairly potent prison.
- Buried Alive: How he is defeated in The Last Olympian.
- Cessation of Existence: Tartarus absorbs his and Krios' essences in The House of Hades.
- The Dragon: Second-in-command to Kronos, is the only one fighting in the Battle of Manhattan with him, and is the second most powerful.
- Elemental Powers: He has fire and light powers.
- Light Is Not Good: The Titan of Light (and uses light and fire-based powers), but very evil.
- The Power of the Sun: As the Titan of Light.
- Butt-Monkey: He thinks of himself this way.
- Cessation of Existence: Absorbed by Tartarus in The House of Hades.
- The Dark Chick: Feels like his abilities are being Overshadowed by Awesome.
- The Resenter: To the other Titans.
- Star Power: Though the extent of his power is not known, since his battles are never described.
- Villain of Another Story: The Lost Hero reveals he was off defending Mount Othrys from the Romans.
- What Happened to the Mouse?: Before The Heroes of Olympus series is released, his fate is left hanging, as he is the only Titan to be introduced but not be faced by the heroes. The Lost Hero clears this up right away by Jason claiming that he personally defeated Krios while the Romans were attacking Mount Othrys.
- Adaptational Villainy: In the original myths, he one of the few Titans (other than Prometheus and his brother) explicitly stated not to take part in the Titanomachy. Poseidon takes notice of this and states this only proves how bad things really are, as Oceanus wouldn't have joined forces with Kronos if he didn't feel confident in him winning.
- Horned Humanoid: Has bull horns.
- Making a Splash: Part of his domain. He was the supreme ruler of the sea before Poseidon was born.
- Our Mermaids Are Different: Mainly takes shape of a merman, though he does able to change into humanoid form.
- Screw This, I'm Outta Here!: After Kronos' defeat, Oceanus escapes back to the ocean. Why Poseidon doesn't pursue him is unknown, but they may rule different parts of the sea.
- The Siege: Launches a siege against Atlantis in The Last Olympian. He manages to conquer it after Poseidon leaves to assist the battle against Typhon, but he releases it once Kronos is defeated.
- Adaptational Villainy: Again, like Oceanus, a Titan who's on the gods' side in the first war is turning their back in favor of the Titans. Although it's pointed out he's at least partially doing it out of revenge for Zeus chaining him to a rock and having a vulture eat his liver every day for centuries. For some reason, he's also totally cool with Kronos' plan to kick humanity back to the stone age, when in the original myths his defining trait was caring for humanity so much that he defied Zeus to give them fire.
- Affably Evil: If one can call him evil.
- I Fight for the Strongest Side: He's foreseen that the Titan's will win the war and this is why he's on their side.
- If My Calculations Are Correct: Implied that part of his foreknowledge is his ability to calculate probability to predict the most likely outcome.
- Know When to Fold 'Em: After Kronos's defeat, he went into hiding and sent a list of excuses to Zeus explaining his actions. According to Hermes, Zeus probably won't punish him, as long as he keeps his head down for the next few centuries or so.
- Revenge Before Reason: One possible interpretation of his defection. He himself doesn't even deny he wants revenge when Percy brings it up.
- Scars Are Forever: Thousands of years after Hercules freed him he still has the scars from the vulture that tortured him every day during his punishment. Percy compares their appearance on his human-sized form like he was attacked by a very angry hamster.
- The Smart Guy: Among the Titans who appear, he's the most intelligent and predicts the Olympians' loss this time.
Gods
- Foreshadowing: Janus is a Roman god. Among a world that's been so far established to be Greek through and through. Gee, wonder why is that...
- Multiple Head Case: He has two faces, each of which has its own mind.
- Sadistic Choice: His favorite kind.
- Two-Faced: He has a face on the left and right sides of his head.
- BrotherSister Incest: Her husband is her brother, Phorcys.
- Monster Progenitor: She gave birth to Ladon, the skolopendra, the gorgons, and the Grey Sisters. Her most notable child is Echidna, herself an infamous Monster Progenitor, making Keto the proud grandmother to a whole host of nasties.
- Dead Person Impersonation: As the goddess of ghosts, she can take on the appearance of anyone who has died.
- Sadist: She sided with Kronos because Hades won't allow her to torment mortals during the day.
- Two-Faced: All the way down her body. One side is pale and bloodless, the other black and mummified.
- Convenient Coma: He can put people to sleep for months at a time if it suits him.
- The Faceless: He has a face, but it's blurry and constantly shifting so no one can actually remember it.
- Forced Sleep: If he doesn't want you awake, you won't be.
- Psychic Dreams for Everyone: He's the one responsible.
- BrotherSister Incest: With Keto.
- Monster Progenitor: He's the father of Keto's various children.
- Silly Walk: He moves much like a crab.
- Edible Ammunition: Throws food at Percy when he only weakly responds to her rant.
- Living Statue: Only appears as an angry living statue.
Monsters
- An Axe to Grind: When he wields a weapon it's a double bladed battleaxe.
- Back for the Finale: He returns in The Last Olympian.
- Battle Trophy: His horn is left behind after Percy kills him with it. Once he regenerates, he returns the favor by collecting the camp necklaces of the half-bloods he kills.
- Foe-Tossing Charge: His favored tactic.
- Half-Human Hybrid: Half human, half bull.
- Impaled with Extreme Prejudice: How Percy kills him. Both times.
- Starter Villain: He's the first supernatural being Percy encounters.
- Villain Forgot to Level Grind: Percy's taken several levels in badass by the time they fight again. As a result, the Minotaur is quickly reduced to dust.
- Walking Shirtless Scene: In his first appearance.
- Bears Are Bad News: Two half bears adds up to one full bear's worth of danger.
- Bodyguarding a Badass: They're actually less dangerous than the person they're supposed to guard.
- Dumb Muscle: Neither of them is particularly intelligent.
- Half-Human Hybrid: Half human, half bear.
- Adaptational Wimp: In most myths, the manticore's venom is instantly fatal; by Thorn's own admission, his venom causes pain and paralysis, but won't kill.
- Beware My Stinger Tail: A scorpion tail that shoots spikes.
- Cruel and Unusual Death: Mr. D crushes him to death with grapevines.
- The Heavy: To Atlas for most of The Titan's Curse.
- Mismatched Eyes: One brown and one blue.
- Mix-and-Match Critters: Part lion, part human, part scorpion.
- Near-Villain Victory: He comes very close to killing Percy and his friends.
- Poisoned Weapons: The spikes fired from his tail are poisonous.
- Sanity Slippage: The stress caused by his role in Atlas's army combined with constant failures takes a tole on his mental health. He is calculating and puts on an air of sophistication at the start of the story but behaves nearly as bestially as his appearance by the end.
- Attack Its Weak Point: Only its skin is invulnerable, not the inside of its mouth. For its part, it's entire aware of this trope and tries to open its mouth and eyes as little as possible while fighting.
- Battle Trophy: Its pelt is left behind after its death.
- Nigh-Invulnerability: Its skin is completely impervious to harm.
- All Guys Want Cheerleaders: Unfortunately it's implied to be how she gets her food.
- The Cheerleader: Disguised as one.
- Chuck Cunningham Syndrome: Her sister Kelli reappears in The House of Hades, but she doesn't.
- Gibberish of Love: Her charm causes this.
- Icy Blue Eyes: Only in her human form though.
- Kiss of Death: Tries and fails to entice Percy into one of these.
- Obfuscating Stupidity: She puts on a Valley Girl accent to try and appear harmless.
- Pom-Pom Girl: As part of her cheerleader disguise.
- The Dreaded: Briares is absolutely terrified of her.
- Dual Wielding: She dual wields scimitars.
- Hybrid Monster: She's some combination of gorgon, dragon, and centaur.
- Laser-Guided Karma: She's killed by one of her own former prisoners.
- Poisoned Weapons: One touch from her blades will make you shrivel into dust.
- Wardens Are Evil: Just ask any of her prisoners.
- Attack Its Weak Point: Its armor is nearly impenetrable, but like all crab it has a weak spot on its underbelly.
- Giant Enemy Crab: Natch.
- Airborne Mook: It's the flying equivalent of the Erymathian Boar.
- Pink Means Feminine: It's female and bright pink.
- Alien Blood: It bleeds green.
- Attack of the 50-Foot Whatever: It's a two hundred foot long snake.
- Battle Trophy: Its skin is left behind after it dies.
- Death Glare: Potent enough to paralyze anyone who makes eye contact.
- Eye Scream: Percy stabs out one of its eyes.
- Make Me Wanna Shout: Its roar shatters every window on the block.
- Nigh-Invulnerability: Not a magical variety, it just has really thick armor.
- Plot Armor: A justified in-universe version. It's so dangerous because only a child of Ares can kill it, making any other attempt futile.
- Snakes Are Sinister: It's a giant snake and a key part of one of Kronos's schemes.
- Super Spit: It spits acidic poison.
- King Mook: Queen actually.
- Armies Are Evil: Their Mist disguises look like soldiers, fitting with Atlas's military motif.
- Battle Baton: Their preferred melee weapons.
- Blood Magic: Part of the ritual that creates them.
- Color Motifs: Grey.
- Elite Mooks: They're much more threatening than any of the other monster groups the heroes face.
- Glowing Eyes of Doom: The only patches of color on them are their glowing yellow eyes.
- Let's Split Up, Gang!: They split up to cover more ground.
- Muggles Do It Better: Most of Kronos's warriors use weapons from the era of their birth. The spartoi use guns.
- Nigh-Invulnerability: They're immune to the usual methods of monster killing and can only be destroyed by a child of Hades.
- The Nose Knows: Once they have a scent they can track their prey across a continent.
- Our Zombies Are Different: Unlike the skeletal warriors used by Hades they're their own species rather than animated remains, albeit one with strong ties to the underworld.
- Perpetual-Motion Monster: They never tire in combat or on the hunt.
- Pulling Themselves Together: If you smash them apart they'll just pull themselves together and keep coming.
- Super-Persistent Predator: They never give up once they have a target. The prey can put distance between them through a variety of mundane and magical means, but the spartoi will march after them until the gap is closed. The prey can hide behind magical barriers, but the spartoi will find a way through. In short, the hunt doesn't end without the death of the hunted of the hunters.
- True Sight: They can't be fooled by illusions or invisibility.
- Aquatic Mook: They have the best maneuverability in the water out of any of Kronos's forces.
- The Blacksmith: For Kronos's army.
- The Dog Bites Back: They're bitter about being used and discarded by the gods so they sided with Kronos to overthrow them.
- Kill It with Fire: They're fireproof, so a favored tactic of theirs is to throw lumps of molten metal at foes.
- Monstrous Seal: They look like a combination of seals, dogs, and humans.
- Mooks: Some of them show up as warriors during Kronos's assault on Long Island.
- Poisoned Weapons: Their claws inflict plagues with but a scratch.
- Winged Humanoid: Their general appearance.
Other
- Black Helicopter: Their primary form of transport.
- Blood Knight: Atlas appreciates their violent tendencies.
- Driven to Madness: Some of them are temporarily driven mad by Mr. D.
- Mooks: For Atlas.
- Only in It for the Money: They get paid and they follow orders. Justified, as they don't exactly know about the centuries long mythical conflict and as such can't really choose a cause.
- Private Military Contractors: Their line of work.
- The Unfought: They mainly appear in support roles, while any that actually threaten the heroes are dealt with by others. Justified, as the heroes are all carrying weapons that couldn't harm mortals if they tried.
- Weak-Willed: The Mist and other forms of magical mind control do away with petty moral concerns.