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The seven demigods of the Second Great Prophecy.
- Affirmative Action Girl: Piper and Hazel, when previously Annabeth was the only female protagonist.
- Affirmative Action Legacy: Percy, Annabeth, and Jason are white, Piper is Native American (specifically Cherokee), Frank is Chinese-Canadian, Hazel is black, and Leo is Latino. This is in contrast with the previous series when nearly all the characters were Caucasian.
- Battle Couple: Percy/Annabeth, Jason/Piper, and Frank/Hazel. Other characters note Leo's status as Alone Among the Couples.
- Changing of the Guard: Percy and Annabeth are the only returning characters.
- Conveniently an Orphan: Only Percy's, Annabeth's, and Piper's mortal parents are still around, and the latter two don't exactly have the best relationship with their dads.
- Just a Kid: They are continuously dismissed by their adversaries with this trope.
- Human Mom, Non-Human Dad: Played straight with Percy, Frank, Hazel, Leo, and Jason, but inverted with Piper and Annabeth.
- Rule of Seven: The Great Prophecy mentions seven demigods who will take on Gaea.
- True Companions: Over the course of the series, they slowly, grudgingly grow into this. This is in full force by the end of the fourth book, where they'd willingly risk their lives for another member of The Team.
Perseus "Percy" Jackson
- "Only a thousand times? Oh, good...I thought we were in trouble."
- The Ace: At first, he was presented as this to both the new heroes, who either heard of his greatness (Piper, Jason, and Leo) or experienced his combat prowess firsthand (Frank, Hazel). Also on a meta level to the audience, who know of his five books' worth of Character Development and badassery increase. This is increasingly subverted as the books go on, however, especially in The House of Hades.
- Ambadassador: He was memory-wiped and sent to Camp Jupiter as part of Hera's plan to get the rival camps to trust each other through an "exchange of leaders," trading places with Jason. He was chosen because of his power and general badassery.
- Amnesia Missed a Spot: He remembers only Annabeth, and only very dimly.
- Amnesiac Hero: Along with Jason, as part of Hera's plan, he doesn't remember anything.
- Amnesiac Lover: At the beginning of The Son of Neptune, the only thing he remembers is Annabeth's name. He gets better.
- Badass: So far, the only demigod to basically fight and beat a Giant completely unaided. Sure, there was a god there, but come on. The god in question didn't help at all. note
- Badass Boast:
Percy: Twelfth legion FULMINATA.
- Percy was rather fond of these during the first series, and the trait carries on here. Two particularly memorable ones during The Son of Neptune were:
- Percy to Polybotes, “You. Me. To the finish.”
- The Twelfth Legion Eagle he was holding then shot out a thousand blasts of lightning that basically annihilated the Giants' entire center line due to Percy's willpower. BAD ASS.
- Badass in Distress: Gets taken from Camp Half-Blood and is missing for the entirety of The Lost Hero.
- Babies Ever After: Doesn't actually happen, but he starts thinking about living in New Rome with Annabeth and having kids when he sees all the children running around.
- Batman Gambit: Forces Gaea into helping him defeat Phineas, knowing that she considered him more useful than Phineas. It works.
- Battle Couple: With Annabeth, his girlfriend. The fourth book pits the two of them against Tartarus, and they depend on each other to find their way out.
- Berserk Button: Betrayal. Even the insinuation that he (or his friends) could be traitors is enough to hit this. note
- Big Brother Instinct/A Father to His Men: As in the original series, Percy understands how much more powerful he is than the average demigod, and he is entirely unafraid to use that power to take on entire armies to save his friends and allies.
- Big Brother Mentor: To Hazel and Frank, who are far more inexperienced than he is in Son of Neptune.
- Big Damn Heroes: Riding to New Rome's rescue.
- The Big Guy: Of the non-Dumb Muscle variety. He is this to Hazel and Frank in Son of Neptune, as the only seasoned veteran on the quest.
- Outright stated to be the most powerful of the Seven (now Eight) in The Mark of Athena.
- Broken Ace: His guilt and insecurity about the price of reaching his current status come to a head in The House of Hades.
- Brought Down to Badass: In the Son Of Neptune, he loses the “Curse Of Achilles”. This doesn’t stop him from being a Grade A asskicker and having all his abilities as son of Poseidon under his belt.
- Bunny-Ears Lawyer: Spends a lot of time cracking weird jokes (especially puns) but proves he's still an insanely powerful demigod and warrior. Both Hazel and Piper admit his apparent goofiness misled them.
- The Cape: He's the most powerful demigod of the modern world, The Heart of the Seven and the de facto leader of any group of demigods he winds up with. In the followup crossover story with The Kane Chronicles The Crown of Ptolemy he's the only hero of the four that Big Bad Setne can't find something to tempt with.
- Casual Danger Dialogue: He's very casual with his opponents, even if they're giants.
- Deadpan Snarker: Whenever an opportunity for snark comes up, he takes it.
- Death Glare: Invoked by Percy in Son of Neptune — he uses a "wolf stare" he learned from Lupa to stare people down.
- Did You Just Flip Off Cthulhu?: He mouthed off to Jupiter and got away with it.
- Demonic Possession: Briefly in the third book at the hands of the eilodons.
- Even the Guys Want Him: It's revealed in The House of Hades that Nico had a crush on him.
- Field Promotion: Percy's promotion to praetor, making him a Badass In Charge.
- Fight Magnet: As are all Demigods, though being the son of one of the Big Three, the monsters are attracted to him more than most.
- Figure It Out Yourself: When searching for Camp Jupiter, Lupa can't tell him where he's going — he has to find and get there himself.
- Flat "What.": This is the most he can manage when Nico Confesses he once had a crush on him, then had gotten over said crush in the same breath before blitheley walking away as if he only told Percy what the next day's weather would be.
- The Heart: What Hera/Juno intends him to be for the Seven. The tired phrase about being glue even gets brought up. In The House of Hades, the effects of him not being there are clearly felt among the other characters.
- Heroic B.S.O.D.: When Chrysaor curbstomps him, he falls into a bit of a funk.
- History Repeats: As in the previous series, Percy's deeds are mirroring those of Herakles, Odysseus, and other mythical heroes.
- Homeless Hero: Searching for the Roman camp at the start of Son of Neptune.
- Hurting Hero: Accentuated best in Mark of Athena and Blood of Olympus-being the go-to guy to save the world twice in a row has its prices, namely PTSD, guilt, and extreme fear of failure."Percy didn't feel powerful. The more heroic stuff he did, the more he realized how limited he was. He felt like a fraud. I'm not as great as you think, he wanted to warn his friends. His failures, like tonight, Maybe that's why he had started to fear suffocation. It wasn't so much drowning in the earth or the sea, but the feeling that he was sinking into too many expectations, literally getting in over his head."
- Humble Hero: Despite saving the world less than a year previous, he doesn't make a big deal out of it. This is especially highlighted when he's described from other perspectives: Hazel, Leo, Reyna and Frank view him as intimidating and badass, which is pretty jarring considering his own point of view is usually just casual snark and making everything up as he goes along. They all lampshade the fact that he downplays his heroism.
- Idiot Ball: When Percy forgets the supplies back in the boat and has to go back for them, allowing the karpoi grain demon things to kidnap Hazel. He even lampshades it.
- Indy Ploy: His preferred combat strategy is making things up as he goes along, in stark contrast toAnnabeth.
- Invincible Hero: Has shades of this, even after losing the Curse of Achilles. He's so powerful that Chrysaor is the only person able to go toe-to-toe with him under normal circumstances. Subverted the further he and Annabeth go into Tartarus, where the stakes just get higher and higher and the opponents get more and more powerful. The ONLY reason they survive is that they have a Titan AND a Giant to help them out.
- Ironic Fear: Struggles with a fear of drowning in The Mark of Athena.
- Laser-Guided Amnesia: In the first book, he can't remember anything except Annabeth's name.
- Legendary in the Sequel: Gets a bit of this in The Lost Hero as he doesn't appear but the new characters hear a lot about him from Annabeth and the rest of Camp Half-Blood. (Afterwards he's too busy battling new enemies for anyone to focus on his previous victories). Lampshaded when Piper meets him and doesn't find him as legendary as she expected.Piper: "After hearing so much at Camp Half-Blood about Percy Jackson this and Percy Jackson that, she thought he looked well....unimpressive."
- Let's You and Him Fight: Against Jason while under Demonic Possession.
- Lightning Bruiser: Fast, strong and agile enough to shatter a Roman military formation comprised of other demigods. And all that's without water, which only magnifies these traits.
- Like Brother and Sister: With Hazel in Son of Neptune. He views her as a little sister.
- Living Emotional Crutch: To Annabeth. Finding him is her motivation throughout the first book. Taken to the extreme when both of them are stuck in Tartarus, having only each other to depend on physically, mentally, and emotionally.
- Magnetic Hero: Why Juno picks him as one of the seven. He is unfailingly loyal and inspires loyalty in others.
- Nice Guy: He's all-around a pleasant, supportive, patient, loyal person. Confesses to feeling guilty of, among other things, trying to drown a goddess in poison who had it coming and not checking to make sure the Olympians had freed Calypso, despite spending the majority of his time after the events of the first series in a magically-induced coma and unable to actually do that.
- Obfuscating Stupidity: Percy is smart, it's just that his recklessness and impulsiveness overshadow this, making him look dumb.
- Oblivious to Love: As of The House of Hades, he's completely unaware of Nico's feelings for him. It takes him a few moments to catch on to the meaning of Reyna's words to him in Son of Neptune, in which she basically offers becoming a Ruling Couple with her.
- Official Couple: With Annabeth.
- One-Man Army: Percy + Water = Unstoppable Machine of Destruction
- Out of Focus: In The Lost Hero and The Blood of Olympus. He's still present and important in the latter, but Percy and Annabeth have no chapters narrated from their point of view, likely due to their prominence in The House of Hades. Instead, Nico and Reyna get A Day in the Limelight.
- Pre-Asskicking One-Liner: See Badass Boast.
- Puppy-Dog Eyes: According Piper he looks like a baby seal when he's pleading for something, making her wonder how Annabeth ever won an argument with him.
- Pursued Protagonist: On the run from monsters right in his first chapter of The Son of Neptune.
- Quest for Identity: In Son of Neptune, he attempts to remember who he was before being memory-wiped while trying to stay alive.
- Reunion Kiss: With Annabeth in The Mark of Athena. And then she judo-flips him.
- Sealed Good in a Can: Juno kept him asleep for several months between the first and second books. Percy was not happy about it.
- Shipper on Deck: For Frank/Hazel.
- Spotlight-Stealing Squad: Percy is raised to praetor after fewer than 24 hours total at Camp Jupiter.
- Stern Chase: Percy is running from Gorgons immediately prior to Son of Neptune.
- Tall, Dark and Handsome: Dark-haired, with the good looks of a Roman god.note .
- Team Dad: Shaping up to be like this, since he isn't the official leader of the quests he's going on. Also part of the reason Hera actually wants him on the quest.
- To Hell and Back: Is sucked into Tartarus with Annabeth. This is the majority of their role in The House of Hades.
- Took a Level in Badass: Apparently he learned the Pokemon move Glare while hanging out with Lupa.
- Two Roads Before You: A happy life under the sea, or misery and world-saving.
- Undying Loyalty: His Fatal Flaw from the previous series appears, downplayed, in the third and fourth books: He falls into Tartarus with Annabeth instead of letting her fall by herself. Later, when someone has to hold the elevator button for the Doors of Death and Bob is too incapacitated trying to save his and Annabeth's asses, Percy tries to get Annabeth to go on without him so he can at least die with Bob. Annabeth is having none of it. This trait is so prevalent that the gods and even his fellow demigods had a very real fear that Percy would absolutely refuse to let any of them make a sacrificial call, even if the quest failed and the world was destroyed because of it. In the end, Frank convinced him not to do this.
- Worf Had the Flu: He is the most powerful of the Seven. The only person who can take him in a straight fight in the entire series is Chrysaor, and he is a son of Poseidon himself.
- Why Did It Have to Be Snakes?: Or rather, airplanes. In Son of Neptune, Percy quickly decides he would rather be driving or running from Laistrygonians and heading towards Alaska on the ground, than flying far out of their reach in an airplane. Not that he has much choice in the matter. This is carried over from the previous series, where Percy doesn't want to ride on planes because Zeus might smite him, as a son of Poseidon, for moving in his domain.
- You Are Worth Hell: Chooses to fall into Tartarus with Annabeth rather than lose her again.Percy: We're staying together. You're not getting away from me. Never again.
- "The first lesson every child of Athena learned: Mom was the best at everything, and you should never, ever suggest otherwise."
- Academic Athlete: Spends ninety percent of her time either designing buildings for Olympus, being a straight-A student, or fighting tons of Greek monsters.
- Action Girl: Even with no special powers other than her wits to aid her, Annabeth is quite the terror with a dagger.
- Awesomeness by Analysis: Outwits the ghosts of Mithras's followers just by making observations about the information about their worship decorating the cavern walls.
- Badass: She proves herself to be a competent fighter on more than one occasion, and accomplishes a lot even outside of combat. A shining example is how she defeats Arachne, all by herself, with nothing but her wits and a modified Scheherezade Gambit.
- Badass Bookworm: As a daughter of Athena, she loves knowledge, and is frequently seen with some sort of reading material.
- Battle Couple: With Percy.
- Badass Family: Her mom is the Greek goddess of strategy (a subset of war), her dad is willing to fly in on a biplane to gun down monsters trying to hurt his daughter, her cousin Magnus is the demigod son of the Norse god of kingship, sunlight, and summer as well as an Einherji, a formerly dead hero who has been granted various physical boons and Resurrective Immortality in Valhalla, on top of having the most prominent son of Poseidon in the modern era as her boyfriend.
- Beauty Is Never Tarnished: Despite all the hell they go through in the fourth book, Percy continuously describes her as beautiful, though this could be justified by his bias because of being her boyfriend.
- Chekhov's Skill (or Chekhov's Classroom): The Chinese fingertrap, which she teaches Frank, and is later used in her fight against Arachne.
- Cool Big Sis: To Piper, being the older and more experienced Greek demigod. To Frank as well, in The House of Hades he remembers her being kind, helpful, and patient towards him. As the second best strategist on the team, he looks up to her.
- Cool Sword: Gets a sword made from a drakon's bone in The House of Hades after she loses her knife.
- Determinator: Annabeth never gives up.
- Friendly Enemy: With Reyna, as seen in their conversation in The Mark of Athena — despite being on opposing teams, they view each other as equals and clearly respect each other.
- Guile Hero: Uses nothing but her wits and a modified Scheherezade Gambit against a giant spider.
- Got Volunteered: For the quest to search for the Athena Parthenos, with no chance to say no to mom.
- I Will Find You: In The Lost Hero, the reason she's mostly Out of Focus is because she's searching for Percy.
- Knife Nut: Still uses the knife Luke gave her. She loses it in Tartarus, much to her chagrin, but gets a Cool Sword instead.
- The Leader: Is established as this when the seven heroes finally unite in Mark Of Athena.
- Living Emotional Crutch: To Percy. Finding him is her motivation throughout the first book. Taken to the extreme when both of them are stuck in Tartarus, having only each other to depend on physically, mentally, and emotionally.
- Neat Freak: She keeps the Athena cabin spotless.
- Official Couple: With Percy.
- Out of Focus: In the first two books, since she's not part of the Power Trio in either one (Jason, Piper, and Leo in the first, and Percy, Hazel, and Frank in the second). Averted in the third, where she provides one of the four viewpoints, and who's subplot gives the third book its name. Again in The Blood of Olympus. She's still present and important, but Percy and Annabeth have no chapters narrated from their point of view, likely due to their prominence in The House of Hades. Instead, Nico and Reyna get A Day in the Limelight.
- Red Herring: In The House of Hades, the reader is initially led to believe that she's the one Nico has a crush on. Then when Cupid shows up, it turns out to be Percy, not her.
- Reunion Kiss: With Percy, and in front of a huge crowd of potential enemy forces, no less. Quickly turned into an emotionally-charged judo-flip into the stone pavement, but her boyfriend takes it in stride. He missed her too, after all.
- Revenge by Proxy: Is Minerva's proxy against the Romans.
- Scheherezade Gambit: Plays this against Arachne when trapped with her. It works.
- Sleep Cute: With Percy in The Mark of Athena.
- The Smart Girl: Most of the time to a fault. She was trusted with Daedalus's laptop and spent long hours engrossed in it while aboard the Argo II.
- The Strategist: Athena is the goddess of war strategy, so all her children are good with tactics, and Annabeth especially so. Her plans have a way of coming together.
- To Hell and Back: Is sucked into Tartarus with Percy. They get back out by walking through hell, as well as fighting him
- The Unfavorite: Gets rejected by Athena (and her hat loses its magic!),or rather Minerva, after trying to speak up for working with Rome.
- Violently Protective Girlfriend: For Percy. Her first appearance in the series is almost attacking Jason because she thinks he knows where Percy's gone. Jason is quite reasonably terrified.
- Why Did It Have to Be Snakes?: Spiders, though she still manages to defeat Arachne.
- Also toward the Cyclopes in Tartarus.
- You Are Worth Hell: Percy could've saved himself if he'd let her fall, but accompanies her into Tartarus anyway. She's painfully aware of this in The House of Hades, and briefly thinks that if he died, it would be her fault.
- "I’m the son of Jupiter! I’m a child of Rome, consul to demigods, praetor of the First Legion. I slew the Trojan sea monster, I topped the black throne of Kronos, and destroyed the Titan Krios with my own hands. And now I’m going to to destroy you, Porphyrion, and feed you to your own wolves."
- The Ace: Hazel refers to him as Camp Jupiter's "golden boy."
- Ambadassador: He was switched with Percy, memory-wiped, and sent to Camp Half-Blood as part of Hera's plan to get the rival camps to trust each other through an "exchange of leaders."
- Amnesiac Hero: Got memory-jacked by Juno in order to set up a huge scheme to get the two camps cooperating. Half his motivation to help Camp Half-Blood was to find Hera and get his memories back.
- Amnesiac Lover: Averted. Jason quickly reciprocates Piper's feelings, but he doesn't want to lead her on when he isn't entirely sure how he feels about her (first because of his amnesia, then because it turns out they were never dating in the first place, and then because of Reyna). As of the first chapter of Mark of Athena, he seems to have gotten together with Piper in the time between The Lost Hero and The Son of Neptune.
- Badass: He took on Enceladus and won. What more needs to be said ?
- Big Brother Instinct: When he finds out that Nico had/has a crush on Percy, he takes it upon himself to defend the kid whenever another group member gives him a hard time or says anything derogatory about him.
- Also his reaction when the group reunites with Leo midway through the fourth book: Jason immediately realizes that something is wrong with his friend and asks if he's alright.
- Blow You Away: His dad's powers give him the ability to control wind.
- Broken Ace: In The House Of Hades. He's very hard on himself and can find it difficult to connect to people, but he's getting there.
- Character Development: In The House of Hades, he develops a Big Brother Instinct toward Nico and Leo, and realizes he may not truly belong at Camp Jupiter.
- The Chosen One: The person who Annabeth would find missing a shoe from a prophecy turned out to be Jason, not Percy.
- Close-Call Haircut: Sciron shoots some of his hair off as a display of his prowess. With a Flintlock.
- Cool Sword: Jason primarily fights with a coin that can turn into either a sword or a spear depending on which side it lands on.
- Demonic Possession: Possessed by an eidolon for a short while in the third book.
- Deuteragonist: To Percy's protagonist.
- The Ditherer: Not in general, but after his experience with Camp Half-Blood, he was more-or-less, as stated several times, 'an aimless wind' - he didn't know exactly what he wanted to be - Greek or Roman - or exactly what he wanted to do with his life, and usually he tried to please everyone. Part of his Character Development across the books is learning to make choices on those fronts.
- Easy Amnesia/Laser-Guided Amnesia: Memory-wiped by Hera as part of her plan to unite the Greeks and Romans.
- To Percy. They're both The Ace and natural leaders, but Jason is comparatively straight-laced and rigid where Percy is free-spirited rebellious thanks to their different camps and godly parents. They even look very different, with green-eyed, dark-haired Percy and blond-haired, blue-eyed Jason.
- Bromantic Foil: To Leo, see his entry below.
- Good Scars, Evil Scars: Has a little one on his lip from trying to eat a stapler when he was two.
- Hero of Another Story: He was the champion of Rome during the Titan Wars and probably had gone on many epic adventures as Percy and Co. did. Unfortunately, this makes Jason something of an Informed Ability hero.
- Human Mom, Non-Human Dad: His mother is described in the original series as an eighties starlet with a poofy hairdo. His father, of course, is Jupiter.
- Hunk: His handsome face and muscular body are given much attention (usually by Piper).
- I Am Who?: Part of his Quest for Identity in the first book.
- Icy Blue Eyes: They represent his aloofness, at least initially. The text describes them as so several times. Also, they're the only thing he has in common with his sister.
- Ironic Name: In the sense that his name is derived from Greek (Iason = healer) and he's a Roman.
- Let's You and Him Fight: Against Percy by Demonic Possession.
- Lightning Can Do Anything: Normally he ricochets it off his sword or javelin at the intended target. Sometimes works too well, since Achelous took this card off the table, as zapping him in the river would also have meant frying Piper.
- Long-Lost Relative: To Thalia, his older sister. He disappeared when he was two, and they don't meet again until the events of The Lost Hero.
- Meaningful Name: Yes, just like ''that'' Jason.
- Mysterious Past: In the first book. A new kid who calls all the gods by their Roman names, has a weapon that can slay monsters that's gold instead of bronze, knows how to fight really well and has a strange Roman motto with tick marks burned into his arm? Yeah, something's off.
- New Transfer Student: Jason is technically one at the Wilderness School. The Mist creates fake memories for everybody so they think he'd been there for months already.
- Nice Guy: Doesn't ever get mad when things don't go his way. Being positive comes naturally to him.
- Official Couple: With Piper.
- Only Friend: Is this for Nico in The House of Hades, much to Nico's annoyance. He is the Bob-2 to Nico's Alice-1.
- Raised by Wolves: Literally. He was raised by Lupa, a wolf who trains Roman heroes.
- Red Oni, Blue Oni: The Blue to both Leo and Percy's Red.
- Remember the New Guy: Thalia didn't mention having a brother during the previous quintet — however, it's justified in The Lost Hero that his disappearance not only would have put the Roman-Greek split in jeopardy, but was quite traumatic for Thalia.
- Secret Keeper: As of The House of Hades, he's the only person other than Nico himself to know about Nico's crush on Percy.
- Shock and Awe: Having lightning powers, while draining, is definitely an impressive trump card.
- Straight Man: Because of his seriousness, he's quite deadpan.
- Straight Man and Wise Guy: With Leo.
- The Stoic: He's been a leader since he was young, and since his temperament sets the mood for his followers, he can't afford to get emotional. It's hardwired into him.
- Team Dad: Acts as The Leader of the group due to his Roman upbringing being stricter than that of the Greeks', and in the third and fourth books tries to act as this for everyone else.
- Tell Me About My Father: He asks Thalia to tell him about their mother. He isn't very happy with what he hears.
- You Can't Go Home Again: Even the undead legions in Epirus recognize his subconscious desire to stay at Camp Half-Blood, and thus refuse to recognize him as a praetor. He realizes it himself.
- Wrecked Weapon: Destroyed during the fight with Enceladus.
- "Being a hero doesn't mean you're invincible; it means you're brave enough to stand up and do what's needed."
- Action Girl: She certainly doesn't start out as one, but becomes a bona fide Action Girl able to take on giants by the last book thanks to a combination of luck, raw talent, and swordfighting lessons from Hazel. Her only power is charmspeaking, but its powerful enough to daze enemies, knock people asleep, or reverse a tree's growth. And with her dagger? The giant she saved Leo from won't be messing with anyone soon.
- Affirmative Action Legacy: Native American. Specifically, Cherokee.
- Badass: She can hold her own with Katoptris and save the day with charmspeak, particularly evidenced with the former when she defeats Khione a second time and with the latter when she puts Gaea to sleep.
- Beauty Is Never Tarnished: Discovers in the first book that it's impossible to mess up the magic makeover provided by the Blessing Of Aphrodite, even if she wants to.
- Bound and Gagged: Gets captured and tied up in the first, third, and fourth books.
- Braids of Action: Normally wears her hair in a long braid down one side with a bird feather. Annabeth has no idea where she finds the time to do it aboard the Argo II.
- Charm Person: Like a few other children of Aphrodite, Piper has the ability to 'charmspeak' people, which basically amounts to getting people to do things you want them to do, sometimes without them knowing.
- The Chick: Being the daughter of Aphrodite, when sometimes she thinks of charmspeaking as nothing more than having a "pretty voice", and a dagger that's not really meant for combat? Piper sometimes feels like she falls into this when it comes to the seven.
- Cool Loser: While at school, she has all of two friends and is shunned despite her beauty and personality.Leo: ...if those girls found out the truth about her dad, they'd all be bowing down to her screaming, 'We're not worthy!'.
- Conflicting Loyalty: When her father gets captured for most of the first book, she is torn between saving him (which requires pledging allegiance to Gaea) and risk his life to save the world.
- Deadpan Snarker: Gets a moment of this in The House of Hades:Khione: Jason will grace my throne room.Piper: Clever. Take you all day to think up that line?
- Emotions vs. Stoicism: Because she's Aphrodite's daughter, she tends to play the "emotions" part, especially when paired with logical Annabeth or stoic Jason.
- Everything Sounds Sexier in French: It's the language of love, so she can speak it.
- Fake Memories: Her relationship with Jason was thanks to Mist manipulation.
- First Girl Wins: Introduced as the first person Jason meets on the bus and his girlfriend. It turns out they weren't dating to begin with and it was all just fabricated memories of the Mist, but over the course of the first book they have genuinely grown to have feelings for each other. Despite Jason remembering a girl he was close to back in Camp Jupiter, Reyna, he's gotten together with Piper in the time between the two books.
- Gut Feeling: Has pretty good instincts thanks to being more attuned to people's emotions. This gets her out of the Temple of Fear in The Blood of Olympus, as it was all about following instincts and trusting your emotions.
- Hair Decorations: Wears a feather in her hair with her braid. In the last book, it's specifically a bright blue harpy feather.
- Heart Is an Awesome Power: Ratchets her use of her Charmspeak up to awesome levels in The House of Hades, where she uses it to defeat Zethes, Calais and Khione. Said defeat included using Charmspeak to power up the deactivated Festus.
- And manages to top even that in Blood Of Olympus, when she manages to use her charmspeak to knock out Gaea herself.
- Human Mom, Non-Human Dad: Inverted; her mother is a goddess and her father is a mortal actor.
- I Just Want to Be Normal: Several times Piper wishes she weren't a demigod so she could live a normal life.
- Improbable Weapon User: From Mark of Athena and onwards, she uses a food-shooting cornucopia as one of her weapons.
- Kaleidoscope Eyes: Her eyes are a mix of brown, blue, and green.
- Knife Nut: Wields Katoptris, a dagger once held by the Helen of Troy. It can see the future. It was used as a ceremonial weapon, although it can still kick monster ass.
- Like Brother and Sister: Leo's the annoying little brother she never had. She'll still kill even a giant if they mess with him, though.
- The Load: She feels like this among the Seven, being one of two members of the team without powers directly useful in physical combat — the other is Annabeth, who more than makes up for it with smarts and combat experience. Then she learns she can use her charmspeak in truly powerful ways."Piper had a new entry in her top-ten list of Times Piper Felt Useless. Fighting Shrimpzilla with a dagger and a pretty voice? Not so effective."
- Lonely Rich Kid: Her classmates don't know about her movie star father, and she's shunned because she's "different." Hence her fear and possessiveness over Jason.
- Love Hurts: Finding out your boyfriend has amnesia and that he was never really your boyfriend in the first place is a lot to take in.
- Meaningful Name: The name is Piper. Pied Piper. The Charmspeak, y'know.
- Missing Mom: Aphrodite was absent from her life for a long time, and Piper is not happy about it.
- More Than Mind Control: The key to using her charmspeak powers properly, as she works out in the fourth book.
- Mundane Utility: Uses her cornucopia to pop out food for her picnics.
- Noodle Incident: "I'm...not good with cows."
- Obliviously Beautiful: Didn't really realize how pretty she was until she was claimed as Aphrodite's daughter.
- Official Couple: With Jason.
- Offscreen Moment of Awesome: According to Jason, she defeated a flock of harpies on her own some time between House of Hades and Blood of Olympus.
- Plucky Girl: Piper always remains positive despite all the troubles she goes through as part of the Seven.
- Real Women Never Wear Dresses: She seems to have ingrained this into her mentality — she expresses disdain for her more stereotypically feminine mother and siblings and their corresponding ineffectiveness in battle.
- Second Love: May be this to Jason, depending on just how close Jason and Reyna were before he was memory-wiped.
- The Power of Love: Her voice is enough to revive Jason even after his brain's been fried by Hera/Juno's true form.
- Secretly Wealthy: Her classmates never catch on that she's a Hollywood kid.
- Seer: By looking into her dagger like a looking glass. Most of the time it shows her the most horrible parts of her present and future. At one point she wonders how Helen of Troy stayed sane with it...and then realizes that she probably didn't.
- Spoiled Sweet: Is the daughter of famous actor Tristan McLean and isn't very spoiled, other than her justified desire to spend some quality time (that is, longer than five minutes) with said busy parent without any interruptions.
- Sticky Fingers: She's a kleptomaniac on record — however, this was only to get attention, and she wasn't consciously stealing, just using her charmspeak.
- Tomboy: Piper despises stereotypically girly things.
- Took a Level in Badass: She takes swordfighting lessons with Hazel in House of Hades and gradually becomes more skilled with her charmspeak, to the point of being able to put Gaea herself to sleep so she can be finished off.
- Tsundere: She's usually pretty nice, but can be snappy.
- Two Girls to a Team: After Annabeth falls into Tartarus with Percy at the end of Mark of Athena, she and Hazel are the only girls on the Argo II for most of The House of Hades. They end up bonding over this.
- Unkempt Beauty —> Beautiful All Along/She Cleans Up Nicely: After she receives Aphrodite's blessing, which gives her an entirely new makeover that only lasts temporarily.
- Unnecessary Makeover: An in-universe example according to Jason — she was already lovely before Aphrodite's claiming gave her a makeover.
- The Unfavourite: She feels like she's become this to Aphrodite after hooking up with Jason, because having successfully become the girlfriend of the guy she's in love with, she's become less interesting as a person to her mother (who outright says that she thinks of the Seven as stories, as opposed to actual people).
- "Well Done, Daughter!" Girl: Rarely got to spend any real time with her dad. She stole things to get his attention, and has a game that they play in place of bonding, initially.
- What Would X Do?: After Annabeth falls into Tartarus with Percy, Piper finds herself wondering what Annabeth would do in her situation of defeating Khione, Zethes, and Cal.
- "Delaying death is my favorite hobby."
- Affirmative Action Legacy: He's Latino and taking his cues from his father, the Greek Hephaestus
- All Girls Want Bad Boys: Mocked with Narcissus's nymphs — he pretends to be a loud and obnoxious "bad boy" who thinks he's better than Narcissus to distract him and the nymphs from noticing Hazel stealing the bronze.
- Alone Among the Couples: In books three to five, where everyone else is paired off. That said, Leo has crucial ties to all three of the couples.
- And the Adventure Continues: In the final scene of the entire series, he and Calypso fly off into the unknown atop Festus.
- And This Is For...: "THIS IS FOR MY MOTHER, ESPERANZA VALDEZ!"
- Badass: His powerful fire abilities and great mechanical genius easily qualify him for this trope.
- Back from the Dead: Administers the physician's cure on himself after dying while stopping Gaea, bringing him back to life.
- Bag of Holding: Leo's magic toolbelt. It can hold anything that fits into his pockets, and can produce anything that would reasonably be found inside of a garage. As well as breath mints.
- Beware the Nice Ones: Leo is the most friendly and cheerful of our new characters. He is also one of the most dangerous, having powers he can't always control.
- Bromantic Foil: Jason's best friend. He's also louder, funnier, wirier, and more into girls.
- Calling the Old Man Out: He talks back to his dad in a way that not even Percy Jackson would've, and he doesn't even get struck down- if anything, it actually gets him respect.
- Casanova Wannabe: Leo is fond of hitting on pretty girls out of his league. In The House of Hades, he laments not being as hunky as Jason, because that would have gotten him out of his current situation.
- The Chessmaster: Rebuilt the body of the machine dragon Festus inside the hull of the Argo II, then installed the physician's cure into the dragon so it could bring him back to life, as Festus was the only thing capable of surviving Leo's Heroic Sacrifice when he blew himself up to take out Gaea. This also got him around the rules of Ogygia, as the island can only be found once in a lifetime by a demigod, but Leo died and then came back. Nobody figured this out, not even Annabeth, and his death only registered on Nico's radar as odd, not false.
- Dark and Troubled Past: Apparently accidentally killed his mother with his fire powers. He also had a divine grandma who (sort of) tried to kill him several times. Not to mention Gaea messing with his head.
- Demonic Possession: He gets possessed by an eidolon, which makes him open fire from the Argo II onto New Rome and incurs the fury of the Romans against the Greeks.
- Drop the Hammer: Sometimes uses a sledgehammer in combat.
- Dying Momentof Awesome: Leo goes thermonuclear to kill Gaea. He got better.
- The Engineer: Like all of Hephaestus's kids, he's good at building and fixing, but Leo's an especially prodigious one. He kept Festus going and built the Argo II.
- Everyone Knows Morse: Leo learned it from his mother as they used it to keep track of each other when at her workplace. Only Leo is shown to know it and it doesn't serve any real plot relevant purpose except when Festus gives Leo a final message.
- First Kiss: For all of Leo's flirting, he's never been kissed until he leaves Calypso's island.
- Gadgeteer Genius: Even when Leo's doing nothing in particular, he still can fashion incredible machines. When he puts his mind to something, he can make automatons or huge warships.
- Generation Xerox: He’s a dead ringer for his great-grandfather, Sammy Valdez.
- Grease Monkey: As the team mechanic, he's always running around greased due to constantly fixing things.
- Heartbroken Badass: Becomes this around three quarters of the way through The House of Hades after he ends up on Calypso's island, falls in love with her, and then is forced to abandon her. He is noticeably different for the rest of the book, less twitchy, more serious, and well, in the words of Jason:
- Height Angst: He is short and skinny, which does a number on his self-esteem, especially with his male compatriots all being tall and muscular save Nico.
- Heroic Sacrifice: Dies defeating Gaea, which was part of his plan all along. Fortunately, that plan also involved resurrection via the physician's cure.
- Heroic Vow: It ends up being "the oath to keep with a final breath" of the Prophecy of Seven."I'll come back for you, Calypso. I swear upon the River Styx."
- Human Mom, Non-Human Dad: His dad is Hephaestus.
- Identical Grandson: He resembles his great-grandfather, Sammy, so much that Percy and Hazel think he's actually Sammy when they first get a look at him.
- I Let Gwen Stacy Die: He blames himself for his mother's death, which was especially scarring.
- In Love with Love: Leo pretty much falls for any girl who's out of his league, namely Khione and Thalia. Though, he gets over Khione rather quickly when she reveals herself to be a villain. This trait disappears after his first visit to Ogygia.
- Infinite Supplies: That toolbelt of his is enchanted to "contain anything that could be found in a garage", which includes everything from small tools and materials, to a sledgehammer, to taco ingredients, to breath mints.
- Improbable Aiming Skills: Hits an elevator button from thirty feet away by chucking a screwdriver like a throwing knife.
- Just Friends: With Hazel.
- Ladykiller in Love: "Ladykiller" may be a bit overstating it, but after his first visit to Ogygia, he completely stops hitting on other girls.
- Last Words: "And by the way-I love you guys."
- Like Brother and Sister: With Piper. Despite her beauty, he never hits on her or asks her out, and they treat each other like affectionate siblings.
- Keet: He's fun-loving and always full of energy and good times. He's got so much nervous energy that he's got to constantly keep his hands moving. It has even been noted that his ADHD is still exceptional, even for a demigod.ALL DA LADIES LUV LEO
- Kill It with Fire: When Leo starts bringing out the fireballs, start running — as Khione and Gaea herself find out.
- MacGyvering: Being a child of Hephaestus, tinkering and building comes naturally, but he also has an infinite supply of tools (due to his tool belt) as well as his fire-controlling ability (which he uses to bake bricks and weld metal). Heck, when he crash-landed on Ogygia, literally all Leo had were the clothes on his back, his tool belt, and the Archimedes Sphere. He managed to cobble together a very slap-dash but functional personal helicopter in about thirty seconds. It chugged along for a few seconds before promptly exploding, but at least the blast saved him from becoming a bloody splat on the beach below.
- Man on Fire: The first child of Hephaestus to be born in decades with the ability to summon fire. It only makes Leo more nervous since not only does he have a fifty percent chance of destroying the world, but he could also very easily kill another member of the seven.
- Mayfly-December Romance: He falls in love with Calypso, a Titan's daughter and goddess who's been around for millenia.
- My Greatest Failure: After he thought that he killed his mom, Leo didn't want to use his fire powers ever again before his quest with Jason.
- The Nicknamer: To his friends' frequent annoyance.
- Playing with Fire: Leo is the first son of Hephaestus to have this ability since 1666.
- Plucky Comic Relief: Always count on Leo to be able to diffuse the tension or solve problems by being his goofy self.
- Playful Hacker: He apparently once hacked a copy of Mario Party 6 and added a fourth difficulty: Idiot Mode. Basically Artificial Stupidity Turnedupto Eleven.
- Replacement Goldfish: Hazel worries about seeing him as a replacement of her first boyfriend Sammy, his great-grandfather. She seems to be moving past it by the fourth book.
- The Runaway: Ran away from home six times.
- Sad Clown: He smiles and jokes since its easier than being sad about things he can't change or that scare him. Subverted, since Jason notes how important Leo's sense of humor is to team morale.
- Self-Made Orphan: This is the reason why he is initially afraid of his fire powers: when he was a kid, Gaia visited the workshop where he and his single mother were, with the firm intention of preventing Leo from becoming a powerful enemy; he used his powers to try and protect his mother, but lost control and started a fire, accidentally killing her instead. He still has his father, but since he's the god Hephaestus whom he only met at 15...
- She Is Not My Girlfriend: Says this almost word-for-word when Calypso assumes that Reyna is the Penelope to his Odysseus (or Annabeth to his Percy, or Elizabeth to his Sir Francis Drake).
- Stepford Smiler: Type A. He's upbeat and friendly on the outside, but melancholy and lonely on the inside.Keep moving. Don't get bogged down. Don't think about the bad stuff. Smile and joke even when you don't feel like it. Especially when you don't feel like it.
- Team Chef: Able to whip up pretty boss veggie tacos anywhere and anytime you could possibly want them. Just ask Piper or Jason.
- Trickster Archetype: He's described as having a devilish smile that makes people go "Don't even think about it!" Probably for good reason.
- "Tactics. That’s my gift from Mars. A battle can be won before it’s ever fought by choosing the right ground."
- Achilles' Heel: His life force is bound to a stick of wood. If/when it burns up, Frank will die.
- Affirmative Action Legacy: Chinese-Canadian, taking over for the Italian Mars.
- Animorphism: The Zhang family gift.
- Badass: He's quite a good shot with a bow and quiver of arrows, and becomes more and more competent over the course of Son of Neptune.
- As of The House of Hades, Frank is full-on sprinting after Percy with all the level grinding he's gotten in.
- Bad Bad Acting: Frank has many talents, acting is not one of them.
- Big Fun: The first thing that jumps out to Percy is that he's like a baby panda.
- The Big Guy: Lampshaded repeatedly. It's easy to lose track of how many times the text refers to him, verbatim, as "the big guy." Further solidified with his One-Man Army stint in the fourth book.
- Calling the Old Man Out: His dad is Mars, and considering his mom died in war, Frank’s not happy about it. See Your Approval Fills Me with Shame below.
- Determinator: Fights to free Thanatos even if it means literally burning his life away.
- Becomes this in full in The House of Hades, taking Jason's place as Praetor, and doing a complete 180 from his first appearance in The Son of Neptune.
- It's directly stated by Mars that Frank will have to save the quest by helping Percy to make a Sadistic Choice that his Fatal Flaw would never let him make. He does it by never letting Percy have the choice in the first place. Frank goes along when Leo enlists him in pulling off a Heroic Sacrifice without the other Greeks and Jason interfering.
- Outright stated that this is why Gaea wants him dead. Because of his sense of duty and self-sacrifice, he's the only one of the seven that she can't manipulate.
- Distressed Dude: Percy pulls a Big Damn Heroes to save him from the Gorgon sisters near the beginning of Son of Neptune.
- Drama-Preserving Handicap: Frank has to be really careful around fire. (He is understandably somewhat uncomfortable around Leo.)
- Mentioned in universe — because of his powers from his mom's side and being Mars' son and having his tactical powers, he has "too many gifts." Ergo, Fate basically decreed he have a limit.
- Embarrassing First Name: Frank's grandmother is the only one to call him by his Chinese name, Fai.
- Everyone Is Related: He’s a descendant of Poseidon on his mother’s side, making him a distant relative of Percy.
- Field Promotion: Jason promotes him to praetor in the midst of a battle in the fourth book.
- From Nobody to Nightmare: His first appearance is as a son of Mars in probatio, belongin to the fifth cohort. By the end of the books he becomes the Legion's Praetor and, as noted above has taken some god-damn levels
- Hearing Voices: In The House of Hades it's revealed Ares's and Mars's voices have been bickering in his head for a while, and is a major factor towards his hostility towards Leo. Given how different those two facets of his father are, it can't have been pretty.
- Heroic Build: The first thing that jumps out to Percy upon his return from Tartarus is that Frank now looks like a football lineman.
- Heroic Self-Deprecation: As his father pointed out, he considers Percy better than him and constantly dumps on himself, at least until near the end when Character Development kicked in and he became more confident.
- Heroic Sacrifice: Subverted, but it's a very narrow thing. See Determinator above.
- History Repeats: This time, it's Meleager's story.
- How Do I Shot Web?: It takes Frank almost until the very end to figure out how to activate his family's gift.
- Human Mom, Non-Human Dad: Mars took a shine to his mom.
- I Got You Covered: Frank to Hazel and Percy while they were escaping from the Zhang residence. Percy to Frank in Alcyoneus lair.
- Immune to Fate: Mentioned as why Gaea is willing to kill him, she can't predict his future, or manipulate him emotionally. His freedom of choice and ability to change also connects to his unique talent, shapeshifting. Notably, he IS cursed with a short life, as a price for his many powers; it's just no one can predict the how and when.
- Lineage Comes from the Father: Played with. Even though he's a son of Mars, Frank's coolest power comes from his mortal mother.
- Military Brat: His mom was in the Canadian military, and was one of the first women to die in combat, according to Frank.
- My Species Doth Protest Too Much: He starts out as a child of the god of war who hates war while all of his siblings are Blood Knights.
- Though Frank is actually truer to Mars's (as opposed to Ares's) stated views on war.
- Official Couple: With Hazel.
- One-Man Army: Was granted the blessing of Mars in the fourth book, temporarily turning him into one of these.
- Scaled Up: In Mark of Athena. He can turn into a dragon at full power, meaning he isn't limited to normal animals.
- Second Love: To Hazel, after Sammy.
- Secret Legacy: Descended from Periclymenus, one of the Argonauts, on his mom’s side.
- Secretly Wealthy: The Zhangs are loaded, but you couldn't tell that by looking at Frank.
- Shout-Out: To Meleager, whose life was tied to a piece of wood and was killed when his mother threw it in the fire.
- Sitcom Archnemesis: With Leo, though it's kind of understandable as Frank's life is tied to a stick and Leo has hard-to-control fire powers. They seem to be moving past it when Leo gives him a fireproof pouch to carry his firewood in.
- The Straight and Arrow Path: Is a really good shot with a bow and arrow, despite this being set in the 2010s.
- The Strategist: Got this as a power from his dad, Mars. He does most of the battle tactics when Annabeth is out of the picture.
- This Is for Emphasis, Bitch!: "Welcome to Canada, idiot."
- Took a Level in Badass: In The House of Hades after managing to defeat every katobleps in Venice, getting taller and buffer. Hazel notes that something's different about his personality, though. And later again when Jason emergency-promotes him to Praetor, giving him command of a full Epirus ghostly legion.
- He worries that his drastic change in appearance and demeanor will make the others treat him differently. Hazel does not mind.
- You Are Better Than You Think You Are: On the receiving end of this from pretty mucho every good guy he meets, it seems to finally sink in at the end of the fourth book
- Your Approval Fills Me with Shame: Feels this way about Mars boasting about him after the war games, but subverted after Mars appears to him in Venice.
- "I'm not choosing one of your paths. I'm making my own."
- Action Girl: Causing precious metal avalanches and holding off the Romans atop Arion with her cavalry sword is just another day for her, being one of the seven.
- Affirmative Action Legacy: African-American. Finding out the Roman demigods sided with the Confederacy in the American Civil War did not make her happy, since her grandmother had been a slave.
- All Girls Like Ponies: Horseback riding is one of her great loves. The Romans look down on her for using a large cavalry broadsword, designed for someone fighting on horseback, because a good Roman is a foot soldier.
- All of the Other Reindeer: Got picked on a lot as a kid in New Orleans. Camp Jupiter wasn’t all that much better.
- Artifact of Death: Capable of summoning gems and metal from the earth, but misfortune comes to anyone who takes them. These cursed rocks don't effects her Cool Horse, who eats the gold she pulls up.
- Notably Laser-Guided Karma to her mom, who wished the "gift" onto her — ruining her life.
- Back from the Dead: Spent 70+ years in the Fields of Asphodel after she sacrificed her place in Elysium to keep her mother out of the Fields of Punishment. Got out after Nico, after discovering that Bianca had already chosen to be reborn, rescues her instead.
- Be Careful What You Wish For: Pulls up cursed riches due to mommy's request gone wrong.
- The Big Easy: Lived almost her whole life in the French Quarter of New Orleans with her mom. Even in her new life, she originally finds it very hard not to spend half her time back there, one way or another.
- Big Sister Instinct: While it's hard to say whether Hazel or Nico is officially the older sibling (Hazel was born first but died at 13 and hasn't aged a full year yet, while Nico is a "few" years younger chronologically but has actually celebrated 14 birthdays), it is not a question that Hazel doesn't appreciate anyone questioning the wisdom of saving Nico's life.
- Blessed with Suck: Her dad's Pluto, so she has control of "all the riches under the Earth". It's a pretty sweet deal, unless a horrible curse wasn't directly tied to how valuable the metals were. So, if you aren't her, touching the metals she summons is bad for your health.
- Cool Horse: Is the only person the Cool Horse, Arion, will listen to (thanks in no small part to her gold-producing powers).
- Curtains Match the Window: Downplayed, she has caramel hair and gold eyes.
- Dark and Troubled Past/Dark Secret: Was forced by Gaea to use her powers to reconstruct Alcyoneus in Alaska.
- Dark-Skinned Blonde: Her hair is described as being caramel.
- Deliberate Values Dissonance: When Hazel and Leo are dealing with Narcissus in The Mark of Athena, she's as enraptured as any of the nymphs. Until he makes a remark about how Narcissus loves "him". Hazel turns up her nose and doesn't think anything of him anymore. She's from the 1940s, so it's a nod to how certain attitudes from seventy years ago are still ingrained in her.
- Dishing Out Dirt: Daughter of Pluto. Unlike Nico, she got the "god of wealth" half as opposed to the "god of death" half. Unfortunately, her power is mostly limited to precious gems and metals. It's also the curse her mother saddled her with.
- Face Death with Dignity: Death tells her point-blank that she should not be helping to free him, and she desperately doesn't want to die again, but she gets the job done.
- Fish Out of Temporal Water: Spent over seventy years wandering the Fields of Asphodel. Nico brought her back.
- Foreign Cuss Word: "As Hazel marched up the hill, she cursed in Latin. Percy didn't understand all of it, but he got son of a gorgon, power-hungry snake, and a few choice suggestions about where Octavian could stick his knife."
- Gemstone Assault: How she usually attacks with her powers.
- Hate Plague: The other reason why it sucks to be a child of Hades/Pluto. Wherever she goes, she is deeply feared and hated by almost everyone around her (save for her close friends).
- Heroic Sacrifice: Killed herself and her mother to stop Gaea from raising Alcyoneus and then gave up Elysium so her mother wouldn’t go to the Fields of Punishment.
- Human Mom, Non-Human Dad: Her mother is a mortal and her father is Pluto.
- Instant Expert: In The House of Hades, when it comes to Mist manipulation — over the course of the book she ends up better than it than a millennia-old sorceress. Hecate, Goddess of Magic, implies this is due to her liminal status.
- It's All My Fault: Alcyoneus coming back to life was directly Hazel's doing. Even though she was forced to by Gaea, Hazel still feels hugely guilty.
- Jedi Mind Trick: Hazel uses the Mist to manipulate people's perception. It's how she defeats Pasiphåe.
- Just Friends: With Leo. She eventually realizes that it isn't fair to see Leo as a replacement for Sammy, and continues dating Frank.
- Like Brother and Sister: With Percy.
- Liminal Being: Doubly, owing not only to being half mortal half god, but having died and come back to life. Hecate (at a crossroads) tell her this gives her power over the veil between the worlds. It's also implied that this is why she is such a prodigy at manipulating the Mist.
- Long-Lost Relative: To somebody we know well from Camp Half Blood. Seems to be a trend in this series. Turns out to be Nico.
- Meaningful Name:
- Levesque means either somebody who served in the household of a bishop, or just bishop. Of ancient Greek origin, curiously.
- Also, hazel trees are sometimes called "hazel witch trees" due to the healing properties of hazelnuts.
- New Powers as the Plot Demands: Can suddenly do sorcery in the fourth book after receiving a blessing from Hecate, with this having never been brought up before and Hazel having received no previous training. It's foreshadowed when her mother reveals that she summoned Pluto with sorcery, but still somewhat out of left field.
- Nice Girl: Her defining trait is her kindness.
- Official Couple: With Frank.
- Older Than They Look: Mentally, anyways. Being a child of Pluto, she remembered everything during her 70+ years in the Fields of Asphodel.
- Pensieve Flashback: Hazel has some pretty powerful "blackouts". She even manages to pull Frank and Leo into them.
- Resurrected for a Job: Nico's intention was for her to correct her mistakes and hopefully achieve Elysium.
- Ragin' Cajun: Lived in New Orleans until she was 13.
- Replacement Goldfish: Technically being Nico's sister, she has shades of this for Bianca, as the latter had been Nico's first choice to resurrect before he found her,
- Self-Made Orphan: She killed her mother and herself to stop Gaea from raising Alcyoneus back in 1942.
- Supernatural Gold Eyes: Justified. She’s the daughter of the god of wealth.
- Team Mom: Percy and Frank start depending on her for comfort in The Son of Neptune.
- Two Girls to a Team: After Annabeth falls into Tartarus with Percy at the end of Mark of Athena, she and Piper are the only girls on the Argo II for most of The House of Hades. They end up bonding over this.
- Unfinished Business: Hazel delayed Alcyoneus' resurrection in the 1940s, but he was alive and kicking by the 1980s, when he massacred Michael Varus and the Fifth Cohort and stole their eagle standard and equipment. One of the reasons Nico brought her back to life seems to have been to defeat Alcyoneus.
- Weirdness Censor: Hecate tells Hazel she will have to learn to control the Mist to make it to the House of Hades.
- What Could Have Been: In-universe example. Had she stayed in New Orleans, Hazel would have grown up to marry her childhood friend, Sammy.
New Rome/Camp Jupiter
New Rome/Camp Jupiter
- "Senatus Populusque Romanus!"
- Ancient Grome: Utterly Averted, the Greek and Roman halves of Western civilization have been opposed since the Trojan War.
- Bling of War: The Legion wields weapons of Imperial Gold, which serves as their equivalent to the Greek-monster destroying metal Celestial Bronze.
- Badass Army: The Twelfth Legion. Ten-year service is compulsory for all demigods and legacies, after which you can retire to New Rome, and even marry and raise a family.
- Superpowerful Genetics:
- Demigods: Children of a god and a mortal. They frequently inherit powers from their divine parent.
- Legacies: Descended from demigods. While they often don't inherit their ancestor's divine gifts, they can see through the mist and use Imperial Gold weapons. Form the bulk of the Legion.
- Men of Sherwood: The Legionnaires are skilled and powerful, regularly standing off against several times their own number of monsters.
- Shock and Awe: The Legion's eagle standard can shoot lightning bolts. This is where the Legion's nickname of Twelfth Legion Fulminata comes from.
- Soldier vs. Warrior: Roman demigods tend to lean towards Soldier, where the Greeks tend to favor Warrior. Neither side is portrayed as universally superior.
Nico di Angelo
Nico di Angelo
- "...The only person who ever accepted me was Bianca, and she died! I didn't choose any of this. My father, my feelings..."
- Aloof Ally: Even when working with the crew in the fourth book, Nico doesn't talk much and prefers to stand off to the side.
- Always Second Best: Narrowly misses being the hero of the last Great Prophecy, then Hazel shafts him out of being one of the Seven.
- Ambadassador: Serves as Hades's main liason to the outside world.
- Animals Hate Him: Apparently, they can sense the death.
- Armored Closet Gay: Since he hasn't defined his sexuality completely; however it's worth noting that he kept claiming to have a crush on Annabeth and the god of love had to drag out an admission that Nico crushed on Percy before Nico and Jason could proceed with their quest. Justified, though, as a demigod son of Hades not even from this century, he felt like it would only ostracize him more.
- Ascended Extra: Goes from Demoted to Extra in the first three books to getting lots of focus in the last two.
- Badass in Distress: At the end of the second book as a result of some Reckless Sidekick behavior investigating the Doors of Death himself, he gets captured by Gaea's forces. He's held captive in a jar throughout the third book until he's rescued.
- Badass Gay: He has (or had) a crush on Percy and he is one of the most powerful demigods in the series.
- Belligerent Sexual Tension: His bickering with Will Solace in the last book is heavily implied to be this, though its ambiguous if it went somewhere.
- Big Brother Instinct: It's hard to say whether he or Hazel is "officially" the older sibling, but Nico clearly loves her a lot, and seems to spend quite a bit of his time at Camp Jupiter talking to her and cheering her on.
- The end of the fifth book reveals that Hazel considers him to be her big brother, cementing this trope.
- Big Sister Worship: Less so than the previous series, but he's still pretty hung up over Bianca.
- Black Sheep: Among the demigods, being a son of Hades and all — he just doesn't fit in. Although Will Solace makes the point that a lot of this is self-inflicted.
- Black Swords Are Better: Wields a sword made from Stygian iron, a black material from the Underworld.
- Broken Pedestal: Downplayed. Percy was the first demigod Nico ever saw in action, and he idolized him up until Percy told him that Bianca was dead.
- Cannot Spit It Out: In The House of Hades, he absolutely refuses to admit he has any feelings for Percy, to the point that Cupid has to force a confession out of him.
- The Comically Serious: Occasionally, his frowning and seriousness at a joke is funnier than the actual joke.
- Cool Sword: Stygian iron, my friends.
- Creepy Good: He is repeatedly described as unnerving and difficult to figure out by the other demigods. His penchant for Stealth Hi/Bye doesn't help.
- Dark Is Not Evil: A child of Hades who can talk to the dead and fights with shadows and dresses in all black? Loyal to the Greeks as they come.
- Defrosting Ice King: Thanks to Jason and Reyna he is considerably less prickly by the end of Blood of Olympus.
- Deliberate Values Dissonance: He was raised in the 1930s, which goes a long way toward explaining why he's so ashamed to admit he had a crush on Percy.
- Demoted to Extra: In the first three books. He plays a large role in the fourth, and gets POV chapters in the fifth.
- Did Not Get The Guy: The guy in question being Percy Jackson.
- Dream Weaver: To a degree. He can travel and communicate through dreams, but not as well as Clovis can.
- Eerie Pale-Skinned Brunette: He was described as olive-skinned in the first series (as his mother was Italian), but his skin paled to white as he spent more time in the Underworld. This carries on into this series. After returning from his capture in Tartarus, his skin is described as "a sickly greenish-white, like the color of tree sap."
- Foreshadowing: At the end of the Battle of the Labyrinth, during the massive battle, Percy notices some monsters break off from the large group and head towards the camp. He calls to Nico to stop them, and Nico summons some undead to take the monsters down. Among the undead: Roman Centurions. At Camp Half-Blood.
- Gayngst: In The House of Hades, it turns out at least part of his broodiness and desire to stay away from others stems from his (unacknowledged and repressed) feelings for Percy Jackson.
- Hates Being Touched: Hates touching others, too; the only person he seems to show any physical affection towards is Hazel. Begins to get over this by the end of the fifth book.
- Heroic R.R.O.D.: Overuse of his underworld powers causes him to flicker like a ghost, and could make him permanently fade into the shadows. Transporting the Athena Parthenos across the Atlantic nearly does it.
- Hide Your Gays: Very downplayed, but although his feelings for Percy are addressed directly, the words "Gay", "Homosexual" or any equivalent are never used, referring it only indirectly as "What I am" or similar phrases. He is also the only couple that is not outright stated to be one (only heavily implied) and gets a No Hugging, No Kissing treatment.
- Hopeless Suitor: In The House of Hades, it's revealed that he had a crush on Percy that started in The Titan's Curse, while Percy and Annabeth have mutual feelings for each other.
- Human Mom, Non-Human Dad: His dad is Hades.
- Hypocritical Humor: He's entirely aware of the hypocrisy when he tries to convince Reyna to talk to him about her problems and when he congratulates Hazel for making the most of her second chance at life. He's genuinely annoyed when he realizes he should take his own advice.
- Incompatible Orientation: With Percy.
- Ineffectual Loner: Nico doesn't really like people and prefers to work alone, but he's forced to work with the Seven anyway. Not that he really minds.
- He gets particularly ineffectual over the course of The Blood Of Olympus, as he's pushing his powers to the brink. He would not have survived the quest without assists from Hedge, Will, various pegasi, and especially Reyna.
- I Work Alone: Mainly because he feels ostracised and tends to push people away. Will Solace tells him off for having this attitude.
- Looks Like Cesare: Increasingly since the previous series. Leo describes his eyes as sad and tired, and accounts this to him having stared into the depths of Tartarus.
- Loner-Turned-Friend: In the previous series, he started out as a friend but became a loner due to Bianca's death. When this series starts he's still aloof and closed-off but willing to work with the heroes, and even becomes the team's Sixth Ranger of sorts in the fourth book.
- Meditation Powerup: The Death Trance allows him to survive with limited air by eating one seed a day to survive. The seeds in question being from pomegranates grown in Persephone's garden.
- Messy Hair: His hair is always overgrown and shaggy.
- Mind Rape: It is heavily hinted that this is what Nico went through as a prisoner of Gaea, to give an idea of how broken Nico was when he was finally rescued, Percy delivers this thought:Nico’s eyes looked like shattered glass. Percy wondered sadly if something inside him had broken permanently.
- Misunderstood Loner with a Heart of Gold: He's seen as creepy by the Romans (and most characters, really) but he does genuinely care. Subverted near the end of the fifth book, where Will Solace points out that none of the Greeks ostracised him, it was his assumption that they would that kept him away. This probably has to do with Nico's sexuality and his divine parentage making him feel like an outcast in every possible way. Indeed, we never see any of the Greek demigods actively push Nico away, though Will is the first one to put his foot down and make it clear that they would be happy to have him around.
- Morality Pet: Hazel. Even at his grumpiest, creepiest, most anti-social nadir, Nico is still affectionate to his sister. When Frank can't imagine Nico acting out of love for anybody, he still thinks Hazel would be the exception.
- Murder by Inaction: In the fifth book, he allows Octavian to kill himself in a manmade comet attempting to stop Jason, Piper, and Leo from defeating Gaea when he could have very easily stopped him, and comforts himself with the thought that some deaths shouldn't be prevented.
- Necromancer: He can summon and control undead legions.
- Necromantic: Non-villainous example. He really wanted to resurrect his older sister Bianca.
- New Powers as the Plot Demands: Lampshaded by Reyna when he sends powerful dreams to the mortals aboard the Mi Amor, hoping to keep them asleep, she wonders if he's always had that ability.
- Nice to the Waiter: Unlike Percy, Nico visited Bob the Titan and spoke with him often, and apparently talked Percy up to him. It serves the dual purpose of saving Percy and Annabeth's lives in Tartarus and getting Percy to realize that he's neglected not just Bob, but Nico himself over the years.
- Only Friend: Jason is this for him in The House of Hades (as Hazel is also his half-sister and his crush on Percy has complicated their friendship quite a bit.) Nico is Alice-1 and Jason acts as Bob-2. This is because he is Creepy Good and a Socially-Awkward Hero, and intentionally pushes people (including Jason) away.
- Opposites Attract: Seems to be the case between him and Will Solace. While Nico is pale with dark hair, and the son of the god of the Underworld, Will is tan with golden hair, and his dad is the god of the Sun.
- Pre-Asskicking One-Liner: Delivers a pretty good one to Lycaon in Blood of Olympus
- "Come get me, you mutt! or do you have to stay like a good dog until your master shows up?"
- The Promise: At the end of the third book, Percy makes him promise to lead the rest of the Argo II to Epirus to retake the Doors of Death before falling into Tartarus with Annabeth.
- Rescue Romance: His crush on Percy started way back in The Titan's Curse when Percy saved him and Bianca from Dr. Thorn.
- The Resenter: He resents both Greek and Roman camps for driving him away, but specifically resents Percy and Thalia for surviving the quest in The Titan's Curse when Bianca didn't. Doesn't help that Thalia went on to become leader of the Hunters, which Bianca had joined before her death.
- Also averted in the case of Annabeth dating his crush. He finds himself utterly unable to resent her, because she's always been kind to him.
- Sixth Ranger: Joins the crew of the Argo II and goes off with them to rescue Percy and Annabeth at the end of the third book.
- Socially-Awkward Hero: Being a child of the most antisocial god doesn't bless one with good social skills.
- Shameful Source of Knowledge: He knows what a katobleps is because he had its Mythomagic card.
- Ship Tease: Has this with Will Solace, the head of the Apollo Cabin in the fifth book.
- Stealth Hi/Bye: Does this often, to the chagrin of his companions.
- Suddenly Sexuality: The House of Hades reveals that he had a crush on Percy that started in the previous series.
- Superhero Speciation: Had some instances of Dishing Out Dirt in the previous series (notably, splitting the ground open to swallow up some skeletons attacking Percy and throwing up a wall of black rock in the Labyrinth to stop some pursuers), but now that this is his sister Hazel's main ability, he sticks to his "god of death" skill set.
- We Do Not Know Each Other: To Percy, who barely buys it. When confronted, he states that it's not his place to help Percy remember who he is.
- Why Can't I Hate You?: Feels this way about Annabeth, as she's both his romantic rival and one of the people who's consistently nice to him.
- Wrong Name Outburst: Well, slip, anyway. He almost calls Hazel Bianca.
Reyna Avila Ramirez-Arellano
Reyna Avila Ramirez-Arellano
- "I mean to save this camp, Percy Jackson. Things are worse than you realize."
- Abusive Parents: Apparently, her and Hylla's father was one, which was why they ran away from Puerto Rico to Circe's retreat.
- Action Girl: As the daughter of a war goddess, she's very handy in a fight.
- Affirmative Action Legacy: Puerto Rican.
- Aloof Dark-Haired Girl: Is described as tall and dark-haired, with a mature and regal aura which she puts to good use as the leader of Camp Jupiter. Deconstructed as she has a Dark and Troubled Past, so she puts up a mature facade and does not allow herself to show weakness in front her subordinates, as they look to her for guidance.
- Authority Equals Asskicking: The praetor of Rome, as well as a spear-wielding badass.
- Badass Cape: As praetor, she wears a purple one. You gotta look good when you're kicking ass.
- Badass Family: She and her sister are daughters of the war goddess, Bellona. One of them at a time is awesome, but when they team up, monsters should run screaming.
- Bait and Switch: Her Official art◊ makes her look almost like a villain.
- Big Sister Instinct: Develops this kind of relationship with Nico in Blood of Olympus during their quest. She even has to remind herself at one point that he isn't her little brother.
- Blade on a Stick: Her weapon of choice is an Imperial gold spear.
- Braids of Action: She wears her hair in a braid.
- Broken Bird: She's hardened from her past and not all too optimistic about herself, though she hides it with stoicism.
- Canine Companion: She's got two dogs that accompany her around.
- Chekhov's Gunman: While not named, she actually appeared as early as Sea of Monsters.
- Cool Big Sis: Eventually, she becomes an older sister figure for Nico during their quest with Hedge to deliver the Athena Parthenos.
- Despair Event Horizon: First she lost her home to and was imprisoned for months by pirates in Sea of Monsters, then was forced to go on the run with her sister, whom she eventually parted ways with. Which was bad enough. Then in Mark of Athena, after waiting for her love interest and best friend, Jason, to return to her and having to carry on the praetorship all by herself for eight months, Jason coming home with a girlfriend in tow and war breaking out between the Greeks and the Romans within the same hour has pretty much destroyed Reyna's hope that anything good will ever happen to her again.
- Determinator: One of her best traits is her will to power through, and it's part of what makes her such a good leader (as she can pass this on to her followers). Despite losing nearly everything in The Blood of Olympus, she refuses to give up on her quest.
- Gondor Calls for Aid: Knowing that Camp Jupiter will soon be attacked, she tells Percy to find her sister Hylla and ask her to help.
- Friendly Enemy: To Annabeth. They're similar in that they are determined, competent leaders who want the best for their camps, and they even seem to get along fairly well when interacting in The Mark of Athena before everything goes to hell.
- Heroic B.S.O.D.: She suffers from this after seeing the ghosts at her old home in San Juan, right after being forced to leave Hylla behind to delay Orion.
- Human Mom, Non-Human Dad: Inverted: Her mother is Bellona, the Roman goddess of war, while her father was a mortal soldier.
- Lady of War: Fits the personality traits, being calm, aloof, collected, and kickass with a spear. As a bonus, she's also the daughter of Bellona, the Roman goddess of war, specifically.
- The Leader: As the praetor for Camp Jupiter.
- Living Lie Detector: They serve as this, too, which makes them very useful when she's interrogating someone.
- Her pegasus, Scipio, is one too. Which makes it all the more tragic when he is killed in the fourth book.
- Meaningful Name: Her name, like the similar-sounding Spanish "Reina," is a derivation of the Latin "Regina" (queen, counsel), and actually does mean "queen" in Filipino. Fittingly, she's the regal "queen figure" for Camp Jupiter.
- My Country, Right or Wrong: Her loyalty is to Rome and Camp Jupiter above all else. When Octavian brands her a traitor for daring to go to the ancient lands she pushes through with her quest because it will benefit the camp.
- Nerves of Steel: She's very restrained, and works very hard not to let any disturbance she might feel show. Even when she's falling into an active volcano, she convinces Nico to shadow-travel them away and boosts his strength to do so.
- Non-Human Sidekick: Her greyhounds, Aurum and Argentum. Their names are Latin for gold and silver, which aptly describe their colors and are the metals the dogs are made from.
- One Woman Army: Piper is convinced of this, at least.
- Only One Name: For the first three books, her surname isn't revealed at all. It's revealed she doesn't reveal it to just anyone.
- Reasonable Authority Figure: Unlike Octavian, she's willing to listen to our heroes, and seems okay with negotiating for peace between the Greeks and Romans — until a possessed Leo fires on Camp Jupiter. Still, because of her tentative friendship with Annabeth, she doesn't skewer the protagonists on the spot, instead letting them proceed with their mission.
- Romantic Runner-Up: Jason gets together with Piper instead of her, and although she doesn't openly bring it up, it's obvious she's not very happy about it.
- Ruling Couple: She points out it might have happened with Jason if he stayed, then offers this to Percy.
- Self-Made Orphan: Her abusive father ended up becoming a mania, a spirit of insanity. At one point he knocked Hylla unconscious with a chair, so Reyna grabbed the nearest weapon- an Imperial gold sword- and ended up 'killing' him to protect both herself and her sister. Reyna considers this to be Patricide, even when Nico tells her that dispelling a ghost is not the same thing as killing a man.
- The Stoic: As a leader of Rome, being serious and unemotional is practically hardwired into her.
- Super Empowering: As a daughter of Bellona, she can lend her strength to her allies and followers.
- Supporting Leader: Not in the main cast, but as the praetor she's supposed to lead the Romans.
- Took a Level in Badass: A cape of all things does this in The Blood of Olympus, when the Athena Parthenos upgrades Reyna's cloak into an aegis.
- The Woman Wearing the Queenly Mask: Has been carrying the leadership of Camp Jupiter on her own for the past eight months and is struggling under the weight of both protecting everybody from the monster attacks and fending off Octavian’s attempts at seizing the other praetorship.
Thalia GraceA daughter of Zeus, lieutenant of the Hunters of Artemis, and a returning character from Percy Jackson and the Olympians. In the first book, she is off searching for Percy alongside the Hunters, but later comes across Jason, Piper, and Leo on their quest. Thalia reveals that she is Jason's older sister, and that his disappearance at the hands of his mother had been the last straw in her stormy relationship with her neglectful mother (alluded to in the previous series).Like Nico, Thalia keeps her powers from the previous series. Similar to her brother Jason, she can control the winds (but has a crippling fear of heights) and lightning.
- Action Girl: Daughter of Zeus and lieutenant of Artemis, as well as being quite handy with a bow and arrow.
- The Ageless: After becoming Artemis's lieutenant, she has effectively become this, remaining fifteen forever.
- Aloof Big Sister: While they're both overwhelmed about their reunion, Jason's a little hurt that Thalia seems to have distanced herself from her life before the Hunters, considering them more her family than him now.
- Back for the Finale: She and the rest of the Hunters pop up again in the fifth book. Several of the Hunters are killed off during the fight with Orion, but we hear secondhand that Thalia is alive.
- Big Sister Instinct: The only reason she didn't run away from her abusive mother sooner was because of Jason. Their mother offering Jason as a peace offering to Hera was the final straw.
- Cool Big Sis: To Jason, although he is physically older than she is.
- Cool Crown: The silver circlet she wears as Artemis's lieutenant pops up in every description of her, presumably because its femininity contrasts with the rest of her punk getup.
- Human Popsicle: For a short time during the battle in the Wolf House.
- Immortality Begins at 20: Or, rather, a day short of sixteen.
- Improbable Aiming Skills: It's implied joining the Hunters has given her already great archery some sort of magical boost, resulting in this trope.
- Ironic Fear: Her fear of heights is ironic considering she's a daughter of the lord of the sky. Heck, her little brother can even fly, and it's suggested that the only real reason she can't is that she psyches herself out.
- Older Than They Look: She looks fifteen, but is in her twenties.
- Perky Goth: She still dresses in black and enjoys punk rock and all, but she's much nicer than her appearance suggests.
- Sibling Yin-Yang: With Jason, at least appearance-wise. They're actually quite similar in terms of personality.Reyna's narration: [She] had always thought of Jason as The All-American Boy. Thalia looked more like the girl who robbed all-American boys at knifepoint in an alley.
- Why Did It Have to Be Snakes?: She's afraid of heights.
- "Surrender to Rome!"
- Ambiguously Evil: Well-Intentioned Extremist or power hungry Corrupt Politician?
- Ambition Is Evil: Dead set on becoming praetor so he can order a quest to find the Sibylline Books.
- Asshole Victim: A lot of people, Greek and Roman, in-universe and out, did not feel sorry for him when he got himself launched by a flaming catapult and died. Not even his most loyal bodyguard bothered to warn him that his toga was snagged.
- Commander Contrarian: Disagrees with every decision Reyna makes.
- Corrupt Politician: He manages to win favor in the council by backstabbing everyone else.
- Creepy Blue Eyes: He's got dark blue eyes that compliment his generally creepy appearance.
- Dirty Coward: Best exemplified in Blood of Olympus, in which he intends to destroy Camp Half-Blood through blowing it up without actually having to do any work himself and still being able to claim the glory for it.
- Evil Chancellor: Seems to be acting as one to Reyna, as an active advocate of war against the Greeks. She quickly puts a stop to that. The moment she turns her back, he announces that they're changing their plans.
- Evil Counterpart: To Rachel. He serves the same oracular purpose as she does, but he's creepy and manipulative while she's straightforward and nice. They meet in the fourth book; it doesn't go over very well.
- He's also this to Will Solace, both are descended from Apollo, but while Will who is more of a medic than a seer wants to help makes peace, Octavian wants to destroy the Greeks, Will explains that what Octavian was doing was Not what Apollo would want.
- Famous Last Words: "Goodbye, Gaea! Goodbye, Jason Grace the traitor!"
- Fortune Teller: An augur, specifically, and using his insight into the future to twist Camp Jupiter politics to his advantage.
- General Ripper: Has this relationship towards the Greeks.
- Hoist by His Own Petard: In the fifth book, he dies helping to destroy Gaea. He intended to hog all the glory of defeating her for himself, but instead his clothes snag on the ammunition of the onager he fires. He was able to do something useful for once.
- Jerkass: His rampant hatred of Greeks, hunger for power, and cruelty towards others more than qualifies him for this.
- Meaningful Name: Shares quite a few personality traits with the original Octavian, including ambition and being a smooth talker.
- Number Two: The augur is right below the two praetors in the chain of command, unfortunately.
- Prophecies Rhyme All the Time: In a series that mostly plays this straight, Octavian lampshades it by demanding that the prophecy Mars gives be cryptic and vague. Mars pulls out a grenade.
- Sanity Slippage: Suffers from this to a serious degree in The Blood of Olympus when he essentially dive head first off the deep end and begins recruiting criminals to help his cause.
- Seer: Guts teddy bears to see the future.
- The Starscream: The traitorous second-in-command to Reyna.
- Trojan Horse: Invokes it when he advises the Romans to "beware of Greeks bearing gifts. Subverted, since that wasn't the plan to begin with.
- War Hawk: Is the most vocal in Camp Jupiter about going to war against the Greek demigods, and when Leo, possessed by an eidolon, starts firing on the camp, thereby giving him a reason, Octavian eagerly jumps on it and whips the Romans into a war frenzy.
- Well-Intentioned Extremist: Jury's still out on whether he’s this or just a power hungry bastard.
Will SolaceA son of Apollo. Returning character from Percy Jackson and the Olympians.
- Anger Born of Worry: At the end of Blood of Olympus he's upset that Nico hasn't stopped to rest after the battle with Gaea.
- Ascended Extra: He's a minor character in The Last Olympian, but makes a return as a more prominent supporting character. Taken Up to Eleven in the last portion of The Blood of Olympus, where he partners up with Nico throughout the last battle and afterward.
- Back for the Finale: Along with the rest of the Camp Half-Blood crew in The Blood of Olympus, he shows up during the war scenes.
- Belligerent Sexual Tension: His bickering with Nico in the final book comes off as this.
- Bi the Way: He does in deed get together with Nico.
- Combat Medic: Besides the medical skills, he's also an active participant in the final battle against Gaia and the battles in the previous series.
- Catch Phrase: Downplayed, but twice now he's used "Doctor's orders" to boss Nico around.
- Make Me Wanna Shout: His father's role as the god of music lets him whistle in the ultrasonic range. It's bad enough to stun the entire twelfth legion.
- Meaningful Name: His surname, Solace, contains the word "sol," which suitably for the son of Apollo, is Latin for "sun." Also, "solace" can be read as a verb, meaning that he is someone who "will solace," which corresponds with the potential of his healing talents. He also brings solace to Nico di Angelo, child of death, who is perhaps more in need of comfort, appreciation, warmth, and sunshine than anyone else.
- The Medic: As a child of Apollo, he's skilled with healing. He even delivered Mellie and Hedge's baby, though he was squicked out by it.
- Nice Guy: Although he has to force Nico to accept his kindness most of the time.
- "No. Just... No" Reaction: Basically, the look on his face when a hyper Leo asks him when he will have the chance to use a sword.
- A more serious version occurs when he more or less orders Nico not to use his shadow-traveling ability.
- Non-Action Guy: Admits he lacks many of Apollo's combat skills and his tactic when encountering hostile Romans is to run away and cause a diversion. It's implies this status bothers him.Will: "I wish I was a better archer. Actually I wish I could use any of my father's gifts to stop this war. Unfortunately I'm just a healer."
- Second Love: Implied to be this to Nico, after Percy, as of the final book.
- Ship Tease: With Nico di Angelo, as of the end of Blood of Olympus.
- Surfer Dude: Has the look, though his personality is more Dr. Mccoy Jr.
- Tsundere: His bickering with Nico makes him come across like this.
ClovisA son of Hypnos.
- Animal Motifs: He's described as looking like a baby cow.
- Asleep for Days: Because of being a child of the god of sleep.
- Butt Monkey: To an extent. The last time we see him in The Lost Hero, Butch is trying to see how many pencils he can shove up Clovis's nose. Twenty.
- Dream Weaver: As a son of Hypnos, he spends most of his time in dreams and has a lot of power over them.
- Heavy Sleeper: He's very difficult to wake up.
- Running Gag: Constantly falling asleep.
ButchA son of Iris.
- Everything's Better with Rainbows: His rainbow tattoo, a tribute to his mother.
- Real Men Wear Pink: Read: rainbow tattoo.
Drew TanakaA daughter of Aphrodite and also former head counselor of her cabin. She also appeared in The Serpent's Shadow.
- Alpha Bitch: She fits the general trademarks: snotty, beautiful (she is one of Aphrodite's daughters, after all), and always gets her way. Until the end of The Lost Hero, where Piper kicks her out of the role as head counselor of the Aphrodite cabin.
- Asian Airhead: She isn't the sharpest tool in the shed, to say the least, and she's specifically described as Asian (presumably Japanese because of her surname).
- Bitch in Sheep's Clothing: Acts nice, but it's a only a front for her rather nasty personality.
- Charm Person: She and Piper are the only known demigods capable of charmspeaking as of now.
- Evil Counterpart: To Piper. They're both daughters of Aphrodite and have the rare "charmspeak" ability, but Drew uses it to bend the other Aphrodite campers to her will, as opposed to Piper.
- Gender-Blender Name: A female camper named Drew.
- Girl Posse: Outside of camp, she has one at her school in The Serpent's Shadow of The Kane Chronicles.
- Jerkass: She deliberately antagonizes everyone who isn't on her side.
- Popular Is Dumb: Drew is the Alpha Bitch at camp, but doesn't have the smarts to back it up.
- The Rival: To Piper in The Lost Hero.
- Took a Level in Kindness: Possibly. Although Piper describes her as bratty, she's apparently become at least less enough of a jerkass to be relieved at Piper's survival and return in the final book, though it's also mentioned it's "probably because [Piper] could run things and give Drew more time for gossip and in-cabin beauty treatments".
MitchellA son of Aphrodite.
- Nice Guy: He's friendly to Piper and helps her settle in at the Aphrodite cabin, even when Drew antagonizes her.
LacyA daughter of Aphrodite. Along with Drew, she appears briefly in The Serpent's Shadow.
- Nice Girl: She helps out Piper when she's new to the Aphrodite cabin.
HyllaReyna's sister, and the Queen of the Amazons. Returning character from Percy Jackson and the Olympians, albeit a bit part.
- Action Girl: She leads the Amazons, a job for which this trope is pretty much a requirement.
- Amazon Brigade: Leads the Trope Namer.
- Ascended Extra: Appeared very briefly in Sea of Monsters as one of the girls on Circe's island.
- Asskicking Equals Authority: Any Amazon can challenge the queen to a duel if she wants to take over. It's not clear if this is how Hylla got her position, but we do know that she killed at least one strong challenger — Otrera, the resurrected first Queen of the Amazons. Twice.
- Back for the Finale: Shows up again in The Blood of Olympus, where she and Reyna work out their family issues. Her fate is ambiguous, although it is implied she survived.
- The Cavalry: At the end of Son of Neptune, she leads her army to her sister's aid.
- Human Mom, Non-Human Dad: Inverted, her mom is Bellona.
- Lady of War: A daughter of Bellona, which lends her a stoic, graceful air.
- Red Baron: "Hylla Twice-Kill," after killing a resurrected Otrera twice.
- Straw Feminist: A heroic example, similar to the Hunters.
- Strong Family Resemblance: Looks very much like Reyna.
- You Shall Not Pass: Pulls this on Orion in Blood of Olympus, staying behind in San Juan to fight him so that Reyna has time to escape.
Lou EllenHead counselor of Hecate Cabin at Camp Half-Blood. Makes a brief appearance in The Lost Hero, but gets an expanded role in Blood of Olympus.
- Back for the Finale: Her appearance in The Lost Hero is extremely brief, but her role is expanded greatly in Blood of Olympus, where she fights right alongside Nico and Will during the climax.
- Baleful Polymorph: Can inflict this on enemies with her "pig balls".
- Black Magician Girl: Has the powers, and is definitely a bit of a Troll.
- Cloudcuckoolander/Nightmare Fetishist: For one thing, at the end of Blood of Olympus she tries to keep the group of Roman soldiers that she'd previously Baleful Polymorphed into pigs as pets.
- The Gadfly: Loves to troll her fellow campers. During the counselor meeting in Lost Hero, Jason notices her using magic to play "Got Your Nose" with a fellow counselor's actual nose.
- Master of Illusion: Like, Hazel, she can manipulate the Mist, but isn't quite as good at it.
- Squishy Wizard: Powerful magician, but not much of a close-range fighter.
Halcyon GreenAn elderly son of Apollo. He appears in The Diary of Luke Castellan, from The Demigod Diaries.
- Badass Grandpa: He's old, but is still veritably useful in a fight.
- Heroic Sacrifice: To let Thalia and Luke escape his mansion.
- In-Series Nickname: "Hal"
- Seer: Being a son of Apollo granted him the ability to see the future. However, after he told a girl about her future death, Apollo cursed him by taking away his voice and locking him in his childhood home.
- Tragic Keepsake: He kept the dagger from the girl he saved and passed it on to Luke (who would later pass it on to Annabeth).
Alabaster C. TorringtonDemigod son of Hecate, who fought for the Titans in the last war. He shows up only in Son of Magic, a short story at the end of The Demigod Diaries.
- 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.
- Human Mom, Non-Human Dad: Presumably inverted, since he's a demigod and his mother is the goddess of magic.
- Welcome Back, Traitor: The reason he can't go back to Camp Half-Blood.
DakotaSon of Bacchus, senior centurion of the Fifth Cohort.
- The Alcoholic: Well, not quite...Percy: You let him drink wine?Hazel: Gods, no! That would be a disaster. He's addicted to red Kool-Aid. Drinks it with three times the normal sugar, and he's already ADHD — you know, attention deficit/hyperactive. One of these days, his head is going to explode.
- Heel–Face Turn: He defies Octavian and tries to stop the Roman siege of Camp Half-Blood
- Trademark Favorite Food: Red Kool-Aid.
Clarisse La RueReturning character from Percy Jackson and the Olympians, she's the head counselor of Ares Cabin.
- Back for the Finale: Like the rest of the Camp Half-Blood crew.
- Blood Knight: Always the most eager to fight.
- Demoted to Extra: In the previous series, she was one of the most fleshed-out demigods who wasn't a regular questing partner or friend of Percy's. Here, she just gets a few moments in the first and last books.
- Honorary Aunt: Godmother to Hedge's and Mellie's son, Chuck.
- I Owe You My Life: She is the demigod Hedge saved before going to look for his mother, and she takes that very seriously.
- Masculine Girl, Feminine Boy: See Will Solace above.
- Protectorate: Mellie and her unborn child.
- War Hawk: Repeatedly advocates for the Greeks to just attack the Romans before the Romans attack first.
Bianca di AngeloNico's deceased older sister, from Percy Jackson and the Olympians.
- Posthumous Character: She died in the third book of the previous series, but her death still affects Nico and his relationships.
- Reincarnation: Chose to be reincarnated by the time Nico tried to resurrect her, much to his chagrin.
Luke CastellanA deceased son of Hermes, from Percy Jackson and the Olympians.
- Hero of Another Story: The other story being the previous series.
- Not So Different: Percy recognizes this when he relates his feelings of resentment to Luke's in the third book.
- Posthumous Character: He died in the last book of the previous series, but he is still remembered and mentioned by other characters.
Michael KahaleA son of Venus and centurion of the First Cohort.
- Commander Contrarian: He questions some of Octavian's decisions.
- Everyone Has Standards: As loyal as he is to Octavian, he's sickened by Octavian reinstating Bryce Lawrence.
- Number Two: The second-in-command of Octavian.
- Punch Clock Villain: He's a good guy, but he's very loyal to Octavian, who sponsored his entry into the legion.
- Shoot the Dog: He enables Octavian's death.
Bryce LawrenceA former member of the Twelfth Legion, expelled for his sociopathic tendencies. He is a descendant of Orcus, the god of broken vows and eternal punishment. He is reinstated by Octavian and dispatched to hunt down Reyna.
- The Brute: One of Octavian's "attack dogs."
- Dragged Off to Hell: Courtesy of Nico, who turns him into a ghost and sends him straight to the Fields of Punishment.
- Screw the Rules, I Have Connections!: He would have been executed for his crimes, but his family's influence let him off with exile.
- The Sociopath: Reyna essentially calls him one in describing his sheer remorselessness and bloodthirsty tendencies, not to mention his murder of his cohort, which was why he was expelled in the first place.
- "If I hear about any funny business, I will ground you until the Styx freezes over."
- Ascended Extra: He was mentioned by Grover in a one-liner in The Last Olympian, and is now a major supporting character.
- Badass: Knocked out Keto, a primordial goddess, with a kick to the back of the head in Mark of Athena.
- Blood Knight: He...loves violence. He wasn't bothered that Leo attacked New Rome since it meant fighting.
- Doting Parent: Shows off his new baby boy to everyone from both camps at the final victory feast.
- Extreme Omnivore: He'll eat anything, like most satyrs.
- Fauns and Satyrs: He's a satyr.
- Fearless Fool: He acts like this, being excited to fight even if the odds of winning are next to none because it means violence.
- Happily Married: He and Mellie got married before the Argo II departed.
- Hidden Depths: All the Badass Blood Knight tropes are his characterization from the first three books. In book four, we learn that he and Mellie got married not long before Argo II left, that Mellie's pregnant, that Hedge still feels guilt over not running to his mother's rescue because he was saving Clarisse at the time, and that he's terrified that something will happen to his wife and baby while he's stuck on the other side of the planet.
- I Let Gwen Stacy Die: Revealed in The House Of Hades that while he was bringing Clarisse in to Camp Half-Blood, his mother contacted him in a panic. He couldn't believe anyone would try to hurt a cloud nymph, so he brought the demigod in before looking for his mother. He never found her. Lends his fears for his wife and baby just that extra edge.
- Interspecies Romance: With Mellie, an air nymph.
- Large Ham: Hedge is very loud and flamboyant with his actions.
- Leeroy Jenkins: He's...very eager to go into battle, even if who they're fighting is a potential ally.
- Lineage Comes from the Father: Apparently the son of a satyr and an aura is a satyr. On the other hand, all known satyrs are male and all known aurae are female, so it might be that any daughters would be aurae. Hedge says his own mother was a cloud nymph.
- Noodle Incident: Apparently has nightmares about 101 Dalmatians.
- Official Couple: With Mellie.
- Papa Wolf: He is terrified that he won't be able to save his wife and baby, being stuck on the other side of the Atlantic. When it is suggested that he be one of the three to shadow-travel back to Camp Half-Blood in hopes of diffusing the war, he is elated.
- Team Dad: He's gruff, stern, and attempts to keep the Seven in line in his own way. He's also prone to grounding them.
- Would Hit a Girl: In Mark of Athena, he knocks out Keto, an ocean deity, with a kick to the head.
FestusA dragon automaton and returning character from The Bronze Dragon, an ancillary story from the previous series. At the beginning of the series, he's gone haywire as a result of Beckendorf's death. Currently the figurehead and AI of the Argo II.
- A Boy and His X: With Leo.
- A.I. Is a Crapshoot: In his first two appearances, he's crazed and violent as a result of his damaged control disk. This problem is mostly remedied by Leo later on.
- Breath Weapon: As one might have guessed, he breathes fire.
- Fluffy the Terrible: A giant, firebreathing, flying dragon automaton...named, what is essentially, "Happy." Lampshaded by Jason.Jason: You named him Festus? You know that in Latin, 'festus' means 'happy'? You want us to ride off to save the world on Happy the Dragon?
- Living Ship: Seems sentient. Piper manages to temporarily charmspeak Festus's head into proper sentience in The House of Hades, after which the crew notes he seems more alive.
- Only Mostly Dead: Sliced to pieces by lasers when he crash-lands on Midas's lawn, but this doesn't stop Leo from having Hephaestus take his head back to Camp Half-Blood so he cam become the Argo II's living figurehead.
- Our Dragons Are Different: A robotic one.
- "Words. Words calm Ella down. Words, words, words..."
- All of the Other Reindeer: When she's first introduced, she's being bullied and robbed of her food by the other harpies.
- A Dog Named "Dog": Her name is apparently Latin for..."harpy".
- Back for the Finale: Gets a brief appearance in The Blood of Olympus, and is mentioned at the end to be helping with the effort to translate the Sibylline Books.
- Bookworm: She's read a lot of books.
- Cloudcuckoolander: When she opens her mouth you may hear dangerous, world-altering prophecies...or statistics from horse-races in the 70s, tips on dog-grooming, or how many seasons Friends lasted.
- Cute Monster Girl/Gorgeous Gorgon: Considering harpies are supposed to be ugly old hags, Ella's rather cute◊.
- Does Not Like Cheese
- Encyclopaedic Knowledge: As a result of remembering everything she reads.
- Harping on About Harpies: She is one.
- Interspecies Romance: With Tyson.
- Motor Mouth: Ella is constantly talking about the things she's read.
- Photographic Memory: A variation, with books. Ella can remember everything she reads — just not always when you need it.
- Red Is Heroic: The only red-feathered, as well as nice, harpy seen so far.
- Ship Tease: With Tyson.
ArionSon of Neptune and Ceres, and the fastest horse on the planet.
- Cluster F-Bomb: According to Percy, Arion has a pretty filthy mouth.
- Cool Horse: The son of two Olympians, and as a result can "run like the wind over land and sea."
- Eat Dirt, Cheap: Arion eats gold.
- Jerkass: "I will trample you to death, silly Chinese Canadian baby man!"
- Tactful Translation: We never hear the cursing in full because Percy's the only one who can hear it. The one time we hear him from Percy's perspective, he's too tired to cuss.
- Sir Swears-a-Lot: According to Percy.
- Smug Super: He has an ego to match his top speed.
- Super Speed: Arion is stated to be the fastest horse on the planet. This is apparently not an exaggeration since at one point he does 800 mph.
Iapetus/BobThe Titan of Mortality and Lord of the West, mind-wiped by the waters of the Lethe into becoming a janitor for Hades named Bob. Returning character from The Demigod Files, supplementary material of the original series.
- Almighty Janitor: Literally — he's a Titan, but doesn't remember this and works as a janitor for Hades instead.
- Amnesiacs Are Innocent: He acts very childlike and innocent.
- Amnesiac Dissonance: When he remembers his past, however, he gets darker.
- Anti-Villain: Implied to be this in some of Hyperion's dialogue. Granted, we don't actually get to see any of this during his debut, but then he seemed more happy to rise above his former self in The House of Hades.
- Appropriated Appellation: "I am Bob. I choose to be more than Iapetus."
- Because You Were Nice to Me: The reason he aids Percy and Annabeth. In reality, this was thanks to Nico's doing — he visited Bob in Hades and told him at one point that Percy was a friend.
- Blade on a Stick: His name means "The Piercer", and as both Iapetus and Bob he wields one. It's a standard spear as Iapetus, but as Bob it's a broom with a retractable spear head at the handle end.
- Chekhov's Gunman: He only appeared in a side story to the original series, but later became incredibly important in the fourth book.
- Heel–Face Brainwashing: Due to his dip in the Lethe in The Sword of Hades, Bob's a lot nicer than your average Titan.
- Heel–Face Turn: When he learns of his past as Iapetus, he initially experiences misgivings toward Percy, but ultimately decides to continue assisting them after Percy apologizes.
- Heroic Sacrifice: Decides to side with the heroes at the end, sacrificing his life so they can get out of Tartarus. This weighs heavily on Percy and Annabeth.
- Jerkass: But only as Iapetus. Even then, given Hyperion's words about him being the only one who felt regret about aiding in Ouranos' dismemberment, it's likely he might have been an Anti-Villain.
- Kindhearted Cat Lover: Adopts a skeletal kitten and names it "Small Bob."
- Laser-Guided Amnesia: A fight with Percy, Thalia, and Nico ended with Iapetus getting Lethe river water splashed on his face.
- Messy Hair: Described as Einstein-like.
- Nice Guy: He's kind and helpful to Percy and Annabeth, at least when in his Bob persona. However, he stays nice after finding out about his past as Iapetus, choosing to put it behind him.
- Strong Family Resemblance: Looks like a silver version of his brother Hyperion.
- Token Good Teammate: Among his four brothers he seems to have been this as Iapetus, having been the only one who felt regret about betraying and dismembering their father Ouranos. As Bob, he's without a doubt this.
- "The gods have placed ancient magic on this island to keep me here. A hero can leave. I cannot."
- And I Must Scream: Has been trapped on a island for millenia with no company. The only visitors she ever mentions? Hermes, Hephaestus, Odysseus, Sir Francis Drake, Percy Jackson and the unmentioned one she is telling this to: Leo Valdez. Odysseus was around 1000BCE, Drake the late 1500sCE, Percy and Leo in the early 2000s. Yeah.
- And the Adventure Continues: The very last scene of Heroes of Olympus is her and Leo departing Ogygia for parts unknown.
- Broken Bird: This side of her is explored more than in the previous series; as she's clearly quite bitter after centuries of being alone and under a curse, even after the gods promised to free her from it.
- Curse: Indirectly inflicts one on Annabeth in The House of Hades due to her jealousy over Percy leaving her for Annabeth and bitterness over him not keeping his promise to get the gods to set her free.
- Irony: She curses the gods for sending her someone who she hates, and for not releasing her from her punishment despite their promises to do so. In fact it's implied the Gods arranged for Leo to free her, using the nature of her curse to ensure she winds up with someone she loves. It's even possible they couldn't free her themselves, due to the nature of Gods in this series. But that's what they have heroes for.
- "Leave Your Quest" Test: The island of Ogygia, which is basically a paradise meant to trap heroes.
- Lotus-Eater Machine: Discussed, when she says that "time flows differently" on Ogygia.
- Mayfly-December Romance: With Leo. Though it's left ambiguous whether or not she would remain immortal outside Ogygia, with Leo indirectly bringing this up, Calypso stating that she has no idea... but whether she remains immortal, or will start aging normally, either is fine with her since she is finally leaving Ogygia.
- Smite Me, O Mighty Smiter: Starts doing this once Leo lands on her island, ranting about how the gods are apparently trying to make her suffer even more by sending someone who can't leave and she hates, rather than one who can (and does) but she loves. She may have engaged in this before then too. She isn't happy that the gods haven't set her free yet.
- Slap-Slap-Kiss: With Leo Valdez.
- Took a Level in Jerkass: Downplayed from her previous characterization, with the harsh Tsundere tendencies she displays initially.
- Tsundere: Turns out to be a Type B. From what's seen of her in the previous series, she's a sweet and helpful Nice Girl, but she shows a cranky side towards Leo. Weirdly enough, Leo is the first person to fall in love with her.
- Unrequited Tragic Maiden: Enforced. She's doomed to always fall in love with the hero who washes up on her island, but never have her affections returned, and the heroes cannot leave until she falls in love with them. It's finally subverted when she falls for Leo, who actually reciprocates her feelings.
- Walking the Earth: The Blood of Olympus ends with her and Leo flying off on Festus together to see the world.
- Woman in White: Wears a sleeveless white Greek dress.
- Traits carried over from series one: Adaptational Heroism, And I Must Scream, Misunderstood Loner with a Heart of Gold, Really 700 Years Old, What Could Have Been
DamasenThe Giant counterpart to Ares. As Ares is warlike and bloodthirsty, Damasen is peace-loving and gentle. This put him at odds with the rest of his family, who exiled him in Tartarus. By the time our heroes encounter him, he has become bitter, but they find ways around that.
- Arch-Enemy: Designed to be one to Ares, but this backfired because by being the opposite of a violent war god, Damasen is by default a pacifist without desire to actually fight him.
- Antagonistic Offspring: To Gaea and Tartarus.
- The Beastmaster: With the Drakon at the end of the fourth book. It certainly wasn't on good terms with him before, so it's likely he was exerting some kind of magical control over it.
- Thought it might have just been as eager to break their endless cycle of fighting as Damasen was.
- Big Damn Heroes: Appears during the fight with Tartarus to help Bob hold him off.
- Dragon Rider: During his Big Damn Heroes moment.
- Cynicism Catalyst: Inverted. Seeing the formerly brutal Iapetus rebel against Gaea convinced him that he, too, could change his fate.
- The Exile: Trapped in Tartarus for an eternity.
- Fate Worse Than Death: Exiled in Tartarus for thousands and thousands of years, forever locked in combat with the Maeonian Drakon.
- Hair Decorations: Like the other Giants, but instead of trophies of war, he has grass, leaves and flowers braided in it, reflecting his peaceful nature.
- Heroic Sacrifice: Takes on Tartarus to buy Annabeth and Percy time to escape.
- Let's Get Dangerous: Delivers an awesome speech to this effect whilst battling Tartarus.Damasen: Father, you wished for a more worthy opponent? I am one of the Giants you are so proud of. You wished me to be more warlike? Perhaps I will start by destroying you!
- The Medic: Cures Percy of gorgon-blood poisoning.
- Nice Guy: Because Ares was such a Blood Knight, Damasen ended up being this. His temperament seems to have soured somewhat in the present day, but really, can you blame him?
- No Good Deed Goes Unpunished: For ending the Drakon's rampage through Maeonia (present-day Turkey), he was exiled to Tartarus.
- Red Is Heroic: Has rust-colored hair and cherry-red skin.
- Token Good Teammate: To the Giants.
- You Can't Fight Fate: Initially a believer in this, but Percy and Annabeth change his mind.
- You Shall Not Pass: Against Tartarus, allowing Percy and Annabeth to escape through the Doors of Death.
LupaTrainer of Roman heroes.
- A Dog Named "Dog": Her name is the Latin word for "she-wolf".
- Good Is Not Nice: She's very gruff and stern, and passes this on to her proteges.
- Noble Wolf: Heroic but not nice.
- Sink-or-Swim Mentor: Lupa believes that experience is the best teacher — which is why she basically dumps her kids within fighting range of monsters to see how they do.
- Team Dad: Female example. In contrast to Chiron, who's more hands-on, Lupa is more militaristic and indifferent to the demigods she trains — although she does care deeply about the wellbeing of Rome.
Grover UnderwoodA Protector. He's a close satyr friend of Annabeth and Percy and a member of the satyr council. Returning character from Percy Jackson and the Olympians.
- Demoted to Extra: He's one of the main characters in the previous series, but has a much smaller role in The Heroes of Olympus. The most he gets is some mentions, an appearance in a dream in Son of Neptune, an appearance alongside Rachel in The House of Hades, and a few cameos in The Blood of Olympus.
- Heterosexual Life-Partners: With Percy; he shares an empathy link with him.
ChironTrainer of Greek heroes. Returning character from Percy Jackson and the Olympians.
- Back for the Finale: Appears in The Blood of Olympus during the scenes set in Camp Half-Blood.
- Demoted to Extra: He's a major character in the previous series, but in this one, he appears only in The Lost Hero and The Blood of Olympus.
- Mr. Exposition: Brings Piper, Jason, and Leo up to speed with their heritage and current events.
MellieFormer personal assistant to Aeolus. At the end of The Lost Hero, she replaces Jane as Tristan McLean's secretary.
The Classical Mythology pantheon, featuring more gods than it did last time. As a note, names are written in this form: Greek Name/Roman Name.
- Alternative Character Interpretation: The Roman aspects are this In-Universe — the Romans saw the gods differently than the Greeks did, after all.
- Antagonistic Offspring: Most of them (except for the extremely primordial ones) to Kronos, then to Gaea.
- Ascended Extra: Many of the minor gods, who were just offhand mentions or nonexistent in the previous series, play large roles this time. This can double as Shown Their Work, since many of the Roman gods did have notably different jobs and personalities than they did when they were Greek. See Ares/Mars, Athena/Minerva, and Artemis/Diana for the most extreme examples. Juno, in particular, played a larger role in Roman public and cultural life than Hera did to the Greeks. Vesta was the guardian of Rome (and keeper of the Aegis), while Hestia is almost forgotten.
- Back for the Finale: The Olympians — some of whom haven't been seen since the last series — show up again in The Blood of Olympus.
- Big Damn Heroes: The Olympians show up just in time to help the Seven defeat the giants.
- Broke Your Arm Punching Out Cthulhu: They're in no shape to defeat the giants because they're still recuperating from the last Titan war, with divine schizophrenia from their Greek and Roman sides as icing on the cake.
- Demoted to Extra: Most of the major gods from the last series are laying low this time around, due to the chaos caused by their split personalities.
- Jerkass Gods: As bad, if not worse, than before. A few, like Iris and Thanatos, are exceptions, however.
- Have You Seen My God?: Olympus is closed and the gods have gone MIA per Zeus's orders.
- Inhumanly Beautiful Race: Unless otherwise stated (like in Akhlys's case), or if the narration says they cross into Uncanny Valley despite their beauty, you can expect a god's preferred form will be extremely easy on the eyes.
- Split Personality: Between their Greek and Roman sides, although how bad it is tends to vary — some of the major gods are so incapacitated they have to lay low in order to not inconvenience the world. Other gods, such as Aphrodite and Nemesis, are hardly affected because of their "universal" domains.
- Time Abyss: They've been around since before the fall of the Titans, as they represent humanity's concepts.
- Voluntary Shapeshifting: The gods can take any form they want.
- "You must forge your own path for it to mean anything."
- Ascended Extra: She's a secondary character at best in the previous series, but is much more important in this one.
- Babysitter from Hell: For Leo.
- Character Development: Compared to how she was in the previous series, she's far nicer to demigods. She's shown Jason AND Percy respect and even been supportive, not even getting mad when Percy was basically chewing her out in his dreams. While Jason has some leeway as his Patron Saint, Percy has only the fact that he's one of the seven, and while she could try to boss him around, she's being pretty nice about everything. Though of course you would be nice to a demigod who requested the gods pay more attention to their children (bringing family closer) after saving Olympus. She extended Frank's life as well.
- The Chessmaster: She's been putting her pieces into place for over seventeen years.
- Damsel in Distress: In The Lost Hero, she's held prisoner in a cage at the Wolf House that utilizes her power to awaken Porphyrion and consequently Gaea, hence Jason, Piper, and Leo have to free her.
- Disproportionate Retribution: She seems fond of insane punishments, especially for children of Zeus.Thalia: Save it! You've been nothing but a curse to every child of Zeus for ages. You sent a bunch of intestinally challenged cows after my friend Annabeth!
Hera: She was disrespectful!
Thalia: You dropped a statue on my legs.
Hera: It was an accident!
- Gambit Roulette: She seems to be pulling this considering the whole Jason/Percy switch was her idea. Bonus points for working on this long before the first series, considering her actions with Frank and Leo.
- Karma Houdini: When Piper is both shocked and disgusted to learn Hera caused Hercules to murder his family, but Hercules was the one punished for it, the river god Achelous sadly notes Olympians rarely pay for their crimes.
- Only Sane Woman: Presented as this in The Lost Hero. She is stated to be the primary peacekeeper on Olympus and proposes the compromises that keep Olympus from falling apart thanks to her focus on family and duty. With her missing the egos and personality quirks of the other gods threaten to tear the world apart unless she is returned.
- Patron Saint: For Jason. And of Rome in general.
- Queen Incognito: Juno briefly pretends to be an old hippie lady dressed in trash bags when she dishes out her Sadistic Choice to Percy. She drops the act once they make it to Camp Jupiter.
- Run or Die: The new war has resulted in her being forced to flee from not only the giants, but the gods as well since she's trying to bring the Greek and Roman demigods together. This is because conflict between the two camps lead to severe conflict between the Greek and Roman identities of the gods, the most obvious side effect of which is excruciating pain.
- Teeth-Clenched Teamwork: She knows several demigods (such as Annabeth and Thalia) don't like her, but they're going to have to work together to defeat Gaea and the giants.
- Wicked Stepmother: To all children of Zeus/Jupiter, but startlingly inverted towards Jason. Jason's birth was apparently the last straw for Juno, and Jupiter promised her Jason's life to placate her, naming him after her favorite hero. Why wouldn't Hera be nice to a demigod son of Zeus on the eve of the Gigantomachy? during the last one, Porphyrion nearly raped her until Hercules managed to kill him, which is what caused Hera to accept him in the first place. Maybe she just wants to be sure she'll be saved again.
- "I’m the god of Rome, child. I am the god of military might used for a righteous cause. I protect the legions. I am happy to crush my enemies underfoot, but I don’t fight without reason. I don’t want war without end."
- Blood Knight: Subverted as Mars. He’s not about endless bloodshed without resolution.
- Boots of Toughness: Ares wears them as part of his Badass Biker guise, while Mars wears them as part of a uniform.
- Character Development: He's considerably less of a straight-up jerkass in Son of Neptune, at least in regards to his son. Justified, considering that Mars is held in much higher regards to the Romans than Ares to the Greeks (the Spartans are an exception).
- Colonel Badass: Mars's preferred form.
- Doting Parent: Compared to how Ares treated Clarisse, his Roman counterpart nearly rivals Poseidon.
- Everybody Hates Ares: Averted, he's a mature, dignified, militaristic warrior whom the Romans highly revere. Truth In Television, as Mars was considered the second greatest god after Jupiter.
- Hidden Depths: One might expect that a war god is nothing but a brutal Blood Knight, but Mars is actually very smart and kind of nice. His What the Hell, Hero? speech to Percy in The Son of Neptune is impressive: Mars is the god of war for a just purpose. Ares just likes to brawl. It's the difference between Special Forces and a biker gang. In particular interest is when he gives his son Frank a copy of Sun-Tsu's The Art of War. Percy's response? "I don't think Ares can read."
- Obfuscating Stupidity: Pretends to not remember who Percy is in front of the Romans even though Frank can tell he’s lying.
- Pet the Dog: Keeps Grandmother Zhang company while she’s waiting for Frank to come home one last time.
- So Proud of You: Mars grants Frank his blessing in the fourth book, something he only does to children he's extremely proud of (like Clarisse in the previous series). Well-deserved, as Frank had just killed 200+ monsters with poison breath and poison gazes single-handedly.
- Vitriolic Best Buds: Acts like this with Percy, who's probably a lot more appealing to Mars than he was to Ares.
- "Yes, my children will avenge me."
- Abusive Parents: Not normally, but in Mark of Athena, she shows an incredibly nasty side towards her daughter. Justified in that she was suffering from divine schizophrenia as a result of the Greek-Roman war, like most of the other gods. On top of the stress breaking down her usual logic, Athena has just had all her hatred of Rome stirred up again. She seems to have returned to normal in the final book, where she fights alongside Annabeth to defeat Enceladus.
- Chickification: In-Universe. As a Greek goddess, she had a major role and was a strong warrior. However, the Romans made her a minor goddess who only made crafts, which enraged her. It didn't help that they also stole her statue and hid it for centuries.
- Disproportionate Retribution: The Romans turned her from a major goddess to a minor one and offended her as a warrior. In addition, the Romans stole the grand statue of Athena from her temple in Greece and have hidden it for centuries. She wants all Romans killed in response and has her children keeping the grudge between the two sides going strong.
- Also, in regards to Arachne. Annabeth states that Arachne is a better weaver when compared to Athena, but her true crime was insisting she was better since it was a sign of hubris against the gods. Even then Annabeth thought turning Arachne into a spider was going too far. Going by other comments, Athena is prone to this when someone claims or "is" better than her at something whether it is true or not or is one of her own children.
- Entitled Bitch: Her conversation with Annabeth was just straight up emotional abuse.
- It's All About Me: Her Roman mode, at the very least, seems to be of the opinion that retrieving her statue is of the utmost importance, to hell with any toes she might step on the way. As it turns out, it could be crucial to keeping the peace between the camps.
- Karma Houdini: She is the cause of thousands of years of bloodshed between the Greek and Roman demigods and all of the lives that have been hurt because of it or dragged into it or the wars that were increased because the demigod conflict got involved all over a statue. She is never held accountable and in fact gets her statue back.
- Lady of War: Greek only. This is a major reason for her Disproportionate Retribution.
- Reasonable Authority Figure: She had nothing against Percy while voting him to be killed to stave off the Big Three prophecy and actually consented to Percy/Annabeth (though she does threaten Percy if he mistreats Annabeth.) This does not apply to Romans.
- Revenge Before Reason: To the Romans. Percy's scared of her because this is usually inverted.
- Sore Loser: Is seen as this by Arachne, although whether or not she actually was one at the time is...confusing.
- Ungrateful Bastard: The half-serpent, immortal Kercrops was the first king of Athens, judged the contest between Athena and Poseidon, and ruled in her favor. Athena eventually drove him and his people underground in favor of humans and drove his daughters mad so they flung themselves off a cliff.
- "Beauty is about finding the right fit, the most natural fit. To be perfect, you have to feel perfect about yourself -— avoid trying to be something you're not. For a goddess, that's especially hard. We can change so easily."
- Amazingly Embarrassing Parents: For Piper in The Mark of Athena, where she goes on about romance in front of her, Annabeth, and Hazel.
- Appearance Is in the Eye of the Beholder/Empathic Shapeshifter: As in the previous series, her appearance depends on the viewer's perception of ideal beauty.
- Love Freak: Unsurprisingly, she's very passionate about her domain.
- Love God: One of the most famous examples.
- Hot God: Naturally, as she modifies her appearance to fit the viewer's perception of ideal beauty.
- Obfuscating Stupidity: She only pretends to act like a vapid, giggly klutz.
- Proud Beauty: She's very proud of her attractiveness.
- Shipper on Deck: Even more than in the last series — she doesn't care to hide it for anything. Add Jason/Piper to her list of ships.Aphrodite: Paris and Helen were a cute couple...
- Split Personality: Averted. Love is the same no matter Greek or Roman, so she's not as affected. It also doesn't hurt that she's the oldest Olympian, closer to creation than even the Titans!
Dionysus / Bacchus
- "Did someone just call me the wine dude? Its Bacchus, please. Or Mr. Bacchus. Or Lord Bacchus. Or, sometimes, Oh-My-Gods-Please-Don’t-Kill-Me, Lord Bacchus."
- The Alcoholic: Although as mentioned in the previous series, he's forcibly off the bottle. Bacchus drinks Diet Pepsi instead (versus Dionysus, who drinks Diet Coke).
- Demoted to Extra: His Greek form, who was previously the Supporting Leader of Camp Half-Blood.
- Jerkass: The biggest one of all the Roman gods so far. All of the faults of Dionysus magnified to the point he refused to "help" without a huge tribute. Once he has it, he forces to Jason and Percy to fight the giants AGAIN for his entertainment and only after they have once again killed them does he bother to banish them.
- Miles Gloriosus: Boasts about fighting in the first giant war barely remembering that Hercules did most of the work and he himself defeated the weakest giants. Later, talks as if his killing Otis and Ephialtes was a major victory for him.
ApolloGod of the sun, music, poetry, and prophecy, and patron of the Oracle of Delphi. Twin brother to Artemis. With the onset of the Greco-Roman war, Apollo is trapped with his sister on their home island of Delos, where they are safe from the gods' identity crisis, but unable to lend any assistance.
- Appeal To Vanity: Octavian convinced him to give his blessing by flattering him and promising to make him the favored god of the Romans. Leo uses a similar tactic to get his help later.
- Bi the Way: His own book reveals that he has no problems with dating boys or girls for as long as they please him a trait shared by his son Will.
- Dumb Blond: He usually takes the form of a blond-haired teen, and he's very easily manipulated.
- Foolish Sibling, Responsible Sibling: The Foolish to Artemis' Responsible.
- Hero of Another Story: The sequel series, The Trials Of Apollo, has him as a main character.
- Mis-blamed: In-universe. Zeus holds Apollo responsible for the Prophecy of Seven coming to pass, since Rachel Dare spoke it immediately after he blessed her with the power of the Oracle. Zeus ignores the fact that the Romans had the prophecy for centuries.
- Not That Kind of Doctor: While his domains do include medicine, the specific skills required to create the physician's cure fall under the purview of his son Asclepius.
- Narcissist: Apollo regards himself as perfect and deserving of all praise and being above the other Olympians, including Zeus. He views demigods as tools to make himself look good and is willing to kill them without hesitation if he thinks it will benefit him. The only people he cares about are his mother and sister Artemis. The latter is the only one he is shown to respect and listen to. This bites him big time whenever he angers Zeus, who is more powerful than him.
- Pride: Apollo has an excessively high opinion of himself and abilities even when compared to other major gods. This gets him in major trouble in the last book.
- Sealed Good in a Can: While on Delos, the twins are free of the madness caused by the demigod schism, but unable to affect the outside world.
- That Thing Is Not My Child!: Octavian is his descendant, a fact that Apollo openly laments in Blood of Olympus. He wishes he could have Frank as a son instead.
- Tempting Fate: From The Last Olympian: "Percy, I wouldn't worry too much. The last Great Prophecy about you took nearly seventy years to complete. This one may not even happen in your lifetime." Fast forward a year, give or take, and Percy's in the middle of another Great Prophecy, the onset of which Zeus blames Apollo for.
- Unwitting Instigator of Doom: He gave his blessing to Octavian's plans to make Rome strong again, without realising that his descendant planned to wage war on the Greeks, making him partially responsible for the gods' incapacitation.
- What Happened to the Mouse?: He's confined to Olympus once the Giants are defeated. Since the power of prophecy has yet to return by the end of Blood of Olympus, his fate, and that of the Oracle of Delphi, remain a mystery to the heroes.
ArtemisGoddess of the moon, the hunt, and maidens. Twin sister to Apollo. Trapped on Delos with her brother.
- Daddy's Girl: Zeus has always favored her over Apollo.
- Foolish Sibling, Responsible Sibling: The Responsible to Apollo's Foolish.
- Forced to Watch: She can't leave Delos without succumbing to madness, so she can do nothing to save her Hunters from being massacred by Orion.
- Sealed Good in a Can: Leaving Delos while the demigods are at war will drive her mad.
Poseidon/NeptuneGod of the seas and earthquakes, as well as Percy's father.
- Demoted to Extra: In the last series, he featured more often due to him being Percy's dad, but Percy mentions that the last time he'd seen his father was on his sixteenth birthday. He finally appears in The Blood of Olympus.
Hades/PlutoRuler of the Underworld and father of Hazel Levesque and Nico di Angelo. Has since been given a seat on the divine council after the events of the last series. He laments the unhappy fates of his children.
- Character Development: In the previous series, he was angry and resentful, and downright abusive to Nico, tricking him and telling him how inept he was compared to Bianca. Since then, he's recognized that Nico was right and tries to get Nico to let go of his anger, too.
- Daddy Had a Good Reason for Abandoning You: He doesn't directly acknowledge Hazel after she comes back to life, with others speculating it's so he doesn't have to enforce his own rules and send her back to the Fields of Asphodel. Uniquely, he is also one of the few godly parents who doesn't choose to abandon his kids. Hazel's mom refused him.
- Doting Parent: More to Hazel (as Pluto) than to Nico, Queen Marie talks about how proud Pluto was of baby Hazel, and Hades is coming around. (He gave Nico a zombie!)
- Master of Illusion: Pluto shows some skill with Mist manipulation.
- Parental Favoritism: It's clear he preferred Bianca over Nico, but he's learning to move past this.
Zeus/JupiterLord of Olympus and god of storms, hospitality and justice. He sealed up Olympus before the start of the series, believing it would lull Gaea and the giants back to sleep. The other gods believe it more due to wounded pride at having demigods fight the Titans better than the Olympians and Percy rejecting his offer of immortality. He appears toward the end of Blood Of Olympus to aid in the final battle.
- Bolt of Divine Retribution: Wields the Master Bolt in battle against Porphyrion.
- Head Inthe Sand Management: How the other gods feel he is treating the giant threat.
- Immortal Immaturity: Jupiter is supposed to be a more responsible and mature version of Zeus. However, every story or action attributed to him paints him as virtually the same: a narcissistic, spoiled brat who lets his temper rule him and blames others for his mistakes.
- Jerk Ass: His father-son moment with Jason is ruined by returning to this behavior.
- It's All About Me: Both Jupiter and Zeus hold this view and tend to let it decide things for them letting hurt pride lead to closing Olympus and blaming others for the disaster of the Second Gigantomachy to avoid looking bad. All that keeps him from being easily a textbook Narcissist is he shows a degree of empathy for others Apollos lacks and his status as king and being more powerful than pretty much anyone else somewhat justifies his attitude.
- Karma Houdini: Once again he is the source of numerous problems in the series, but any attempts to hold him accountable fail since he is the most powerful of the Olympians.
- Never My Fault: Zeus blames Apollo and Hera for the second giant war. He claims that Apollo appointing a new oracle who revealed the prophecy, and giving his blessing to Octavian sped up the prophecy, the rise of the giants and the war between the Roman and Greek demigods. He blames Hera for her meddling, which narrowed the possibilities on how the prophecy could have unfolded. He is only partially right since Apollo's blessing ignited the war, and the Fates agree his stance on Hera is somewhat right, However Apollo has little control over new oracles and cannot always control when a prophecy is spoken. On Hera's part, several of the giants had already risen before any of the Seven were born or were even assembled. Following Zeus' plan of doing nothing would have had Porphyrion rising at full strength, Hera no more, and Olympus imploding without her to hold the Olympians together.
- Pride: Stated to be a long running problem with both his Greek and Roman aspects others often have to work around.
- Ungrateful Bastard: Can cough up a "Good job, son" to Jason, but becomes furious with him for daring to question his blaming of Apollo and Hera.
The various winds.
AeolusKing of the winds, weatherman of Olympus.
- Ascended Extra: Was mentioned in The Last Olympian as the one defending the skies of Olympus.
- Blow You Away: He's the most powerful wind god, and as such has domain over winds.
- Cloudcuckoolander: Being the weatherman of Olympus 24 hours a day will do that to you.
- Uncanny Valley Makeup: He was described by Jason as a microwaved Ken doll.
Boreas / AquilonThe North Wind.
- Affably Evil: Definitely not the most antagonistic of the gods, but there's a clear undercurrent of cruel excitement in his discourse with Piper and Jason.
- Arch-Enemy: To Notus.
- Back for the Finale: Per tradition, appears as one of the winds pulling Zeus's chariot in the finale.
- Canada, Eh?: He and his family live in Quebec, Canada.
- Face–Heel Turn: Between appearances, Khione seems to have turned him to Gaea's side. Though this could just be her manipulating his fragile state of mind and body, as he's back on the gods's side by the finale.
- French Jerk: Of the French-Canadian variety, actually.
- An Ice Person: Because he lives in Canada, he is far colder.
- Unwitting Pawn: To Khione.
KhioneBoreas's daughter, the goddess of snow.
- The Bus Came Back: She and her brothers make a reappearance in the fourth book.
- Berserk Button: Never mention Global Warming around her.
- Bitch in Sheep's Clothing: She acts nice, and then her true personality is revealed...
- The Dog Was the Mastermind: Gaea's agent among the Wind Gods.
- The Dragon: Seems to be Boreas' main second-in-command and is much more competent than Zetes and Calais.
- An Ice Person: Displays the greatest prowess in this among the North Winds.
- Manipulative Bitch: Oh, so very much. By the fourth book, she's successfully played Zeus, Hera, and Aeolus for chumps, and convinced Boreas and her brothers to serve Gaea.
- The Mole: For Gaea among the wind gods.
- Spanner in the Works: Thanks to her and her brothers' interference, the Argo II is blown into North Africa and Leo is stranded in Ogygia. Eventually this is all rectified, but the crew loses a lot of time.
- Underestimating Badassery: Shouldn't've dismissed Piper so easily, huh?
- Winter Royal Lady: The goddess of snow.
- Woman in White: Wears a white silk gown.
The BoreadsZethes and Calais, Boreas's sons and Khione's brothers.
- Back for the Dead: Though they can't technically die, their second appearance sees them soundly whupped by Piper.
- Hulk Speak: Cal, who can't say words of more than two syllables and is generally not a fan of sentences.
- Jerkass: Zethes is one of the oiliest and most egotistical characters in the series.
- Villainous Crush: Zethes makes it rather obvious that he's interested in Piper.
- White Hair, Black Heart: Both have stark white hair.
Notus/AusterThe South Wind.
- Arch-Enemy: To Boreas.
- Back for the Finale: Cameos while pulling Zeus's chariot in The Blood of Olympus.
- Brick Joke: During Boreas' rant about Notus in the first book, he makes an offhand mention of his holiday retreat in Cancún. When Notus makes his appearance in The House of Hades, he too says that he has a lovely place in Cancún during the off-season.
- Empathic Shapeshifter: While talking with Jason, his form switches repeatedly between his two identities, mirroring Jason's confusion about whether he belongs with the Greeks or the Romans. When he throws his lot in with the Greeks, Notus's form solidifies for good.
- Hot-Blooded: Notus.
- Two Roads Before You: Auster hates indecisiveness, and insists that he won't help Jason until he decides between Greek or Roman.
- Red Oni, Blue Oni: The Greek and Roman facets of his identity, respectively. Notus is thunderous and ill-tempered, whereas Auster is sluggish and lazy.
- Small Role, Big Impact: At least as far as Jason is concerned, he's the one who solidifies Jason's decision to go Greek.
Zephyros/FavionusThe West Wind, a servant of Cupid.
- Back for the Finale: Pulls Zeus's chariot in The Blood of Olympus.
- If I Can't Have You: Was in love with Hyacinthus and was jealous of the god Apollo's closeness to him, so when Apollo and Hyacinthus were playing a game Zephyros arranged for the disc to strike Hyacinthus. He doesn't seem too hung up about it, though.
- Mysterious Stranger: With a bit of The Watcher, he says that he's been watching Nico for years, knowing that one day he'd have to return to Split and face Cupid.
- Winged Humanoid: His preferred form has two large wings.
Thanatos/LetusThe god of death.
- Compelling Voice: His voice is deep and sonorous.
- Distressed Dude: In Son of Neptune, the whole point of Percy, Hazel, and Frank's quest is to rescue him from Alcyoneus.
- Don't Fear the Reaper: Not particularly gentle and a Scary Black Man with some shades of The Stoic, but obviously not malicious or cruel.
- Good Wings, Evil Wings: Has a pair of black angel wings, specifically.
- The Grim Reaper: As the god of death, this is essentially his job.
- Number Two: Lieutenant of Pluto (Hades). Thanatos acts as border control to keep souls from crossing between life and death without his permission.
- Pretty Boy: Hazel calls him the prettiest man she's ever seen.
- Product Placement: Uses an iPad to keep track of the dead.
- Scary Black Man: Somewhat, although he's just doing his job.
- The Stoic: Merciless and seemingly emotionless.
- Winged Humanoid: His preferred form has a pair of large black wings.
TerminusThe Roman god of boundaries.
- Barrier Warrior: He’s the last line of defense for New Rome.
- Berserk Button: When people don’t follow rules, Terminus gets very, very angry. Also, do not contradict his belief that his statue has arms.
- Butt Monkey: People like to crack jokes at his expense.
- Chekhov's Gunman: Just there for comedy relief? Think again.Percy: (to Polybotes) This is Terminus. He's a god. *WHAM*
- Heart Is an Awesome Power: He has jurisdiction over borders, and this is used in the fight against Polybotes.
Iris/ArcusThe goddess of rainbows and a messenger goddess. She used to run the Iris Messaging service, but has turned over most of it to her assistant Fleecy to focus on running her store and developing an identity of her own.
- Ascended Extra: Doesn't make an actual appearance in the first series, but gets a supporting role in Son of Neptune.
- Did You Just Flip Off Cthulhu?: Enemy forces are surrounding her store, the giant Polybotes leading them. She throws a ding-dong at him.
- Everything's Better with Rainbows: As the goddess of rainbows she's cheery and perky.
- Nice Girl: Unlike virtually every other god or goddess she lacks the arrogance, personality quirks or Jerk Ass qualities that make dealing with the other ones such a pain. She is helpful without having to dance through flaming hoops.
- Granola Girl: She is trying to find her own identity and currently working with an environmentalist-hippie outlook which is what her store represents.
NemesisGoddess of Revenge.
- Death by Irony: A fan of inflicting it. Ask Narcissus...as soon as he stops looking into his mirror.
- Empathic Shapeshifter: She takes the form of those others want revenge on. Leo sees his Aunt that called him a Devil Child for causing her sister's death. Hazel sees her as a long dead Stern Teacher.
- Equivalent Exchange: In the original series, she took one of her children's eyes to influence Camp Half-Blood's victory. In Mark of Athena, she offers the same for Leo, a heavy price for her help should he need it. Leo uses her offer to save Hazel and Frank's lives... which comes at the cost of trapping Percy and Annabeth in Tartarus.
- Split Personality: Averted. Revenge is universal, and her name remains the same whether Greek or Roman, rendering her immune to the debilitating effects of the war.
Heracles/HerculesChild of Zeus who ascended to Godhood as a minor god who guards the doors of Olympus. Previous owner of Percy's Cool Sword.
- Berserk Button: The very mention of Hera will piss him off. He was nice and friendly to his half-brother Jason, hating to give hard quests since he was once a demigod...right up until he mentioned Hera's name. Then he gave them a really hard one and threatened to kill everyone on the Argo II.
- Cool Sword: He owned Riptide before Percy.
- Jerk with a Heart of Gold: Hercules is usually more benevolent towards demigods than most other gods since he knows first hand what a pain it is to constantly go on quests, slay monsters, and put up with the other Olympians. The jerk part comes out with anything involving Hera since she tormented him all his mortal life and upon death he was sent to an island with nothing to do but reflect on his past...which he can never forget.
- Revenge Before Reason: He absolutely refuses to do anything that could possibly benefit Hera in any way. This is pretty justified, considering all the hell she put him through in his lifetime.
- Super Strength: His most famous trait.
- Walking Shirtless Scene: Played for laughs; in the past he was apparently naked so much that the dwarves who stole from him called him "Black Bottom."
- Who Wants to Live Forever?: His immortality means he will never forget the deaths of his first family during his labors and his second one.
AchelousOnce god of the biggest river in Greece; currently stuck on Hercules' island as a punishment (whether it's for him or Hercules isn't clear).
- Abhorrent Admirer: Seems to have been one for Deianara. It's never occurred to him that she didn't want to marry a bull with a human head who lives in a river.
- Anti-Villain: Tries to drown Jason and Piper, but is really kind of pitiable and, to be fair, they were trying to take his other horn.
- Butt Monkey: Lost his wife to Hercules (see Abhorrent Admirer), lost his horn (forever keeping his head off balance) and is now trapped on an island with Hercules, who hates him.
- Making a Splash: You come to expect this from a river god.
- Matter Replicator: His horns become cornucopias after being severed, at which point they shoot out food.
- Mix-and-Match Critters: Human head, body of a bull.
Hecate/TriviaGoddess of magic and crossroads.
- Ascended Extra: Only gets a few mentions in the previous series, but plays an important role in Son of Magic and The House of Hades.
- At the Crossroads: Hecate is the goddess of crossroads, and as such can predict possible outcomes each choice will lead into. In The House of Hades, she shows Hazel three possible outcomes their crew could end up with given their precarious situation, and none of them are pretty.
- Canine Companion: Apparently, she turned Hecuba, the former Queen of Troy, into a Labrador.
- Heel–Face Revolving Door: Born a Titan and served the Olympians in the first war, but is remembered for her stint on the Titan's side in the previous series (although this was pretty justified given how the gods treated her). She's now back on the gods' side, although to what extent is ambiguous.
- Jedi Mind Trick: Notable for being the best Mist manipulator the series has seen so far, due to it being part of her powers.
- Lady of Black Magic: Ur-Example.
- Looks Like Cesare: Beautiful, but deathly pale. Hazel compares her to a dead body.
- Neutral Female: In Son of Magic (a short story in the Demigod Diaries), she stays out of Alabaster's fight against Lamia, and only intervenes when he's about to trap Lamia in her own sand. Justified; she's a god and both Alabaster and Lamia are her children, so she can't play favorites.
- Uh-Oh Eyes: Hazel describes them as black and creepy; although Hecate asserts that she isn't evil, magic, her domain, is merely a tool.
- You Remind Me of X: Tells Hazel that she's a lot like her mother.
AkhlysGoddess of Misery. A resident of Tartarus.
- The Eeyore: As the goddess of misery she's always miserable and self-pitying.
- Master Poisoner: She's also the goddess of poisons, and fittingly has an extensive knowledge of poisonous plants.
- Nightmare Face: Her face is described as horrifying and ugly.
- Required Secondary Powers: Apparently she doesn't have this. When she creates rivers of poison and Percy takes control, they affect her just as much as they did him.
Eros/CupidSon of Aphrodite and god of love.
- Adaptational Badass: This version of Cupid isn't the cherubic winged baby that is normally portrayed. This guy gives Nico and Jason a run for their money and manages to drag out a Nico's suppressed feelings about Percy.
- Combat Pragmatist: Fights Jason and Nico while invisible. As he himself has said, love isn't fair and doesn't fight fair either.
- Happily Married: To Psyche, as per mythos.
- Love Freak: Though in a different sense than Aphrodite. Cupid embodies the less romanticized and deeper meaning of love: The willingness to give up and sacrifice that and for that which you love, and the fact that it's just as capable of making you sad as it can happy.
- Love God: Though this Cupid isn't some love-struck pansy...
- Love Hurts: As the personification of love, he seems to take a dry delight in this trope. That said, he seems to have sympathy for those who are willing to face that it hurts like Nico finally coming clean with his repressed feelings for Percy.Jason: Is this guy Love or Death?Cupid: Ask your friends. Frank, Hazel, and Percy met my counterpart, Thanatos. We are not so different. Except Death is sometimes kinder.
- Man in White: He wears a white suit which only contributes to his harsh beauty.
- Pretty Boy: Jason notes that Eros is beautiful and harsh, like it's difficult to look directly at him.
- Red Eyes, Take Warning: His eyes are blood-red, as if every Valentine was melted down.
- Small Role, Big Impact: He only shows up in one chapter, but what he does in that chapter (forcing Nico to confess he had a crush on Percy in order to defeat him) affects Nico's personality and his interactions with Jason throughout the rest of the book.
- True Neutral: In-universe, self-proclaimed example.Cupid: Love is on every side. And no one's side. Don't ask what love can do for you.
- Winged Humanoid: His preferred form has a pair of wings.
Nyx/NoxGoddess of Night.
- Attention Whore: How Percy and Annabeth manage to talk her down: they pretend to be tourists and that when they booked the "Tartarus excursion" Nyx was hardly mentioned. She doesn't take this very well.
- Casting a Shadow: Part of her power set as the goddess of night is the ability to move in and out of shadows.
- Lady of Black Magic: Ur-Example.
- The Unfought: Thanks to Annabeth and Percy managing to distract her children and cause them to bicker long enough for them to hightail it out of there.
- Whip It Good: Uses a whip made out of stars.
Tiberinus and Rhea SilviaRhea Silvia is the mother of the legendary twins, Romulus and Remus. Her sons were set adrift on the Tiber river. Its god, Tiberinus, saved the twins, who would go on to found Rome, and ended up with her.
- Celebrity Resemblance: They look and act a lot like Gregory Peck and Audrey Hepburn off the set of Roman Holiday.
- Sickeningly Sweethearts: They act giddy and in-love.
TriptolemusA man who found favor with Demeter and was raised to a minor farming god.
- Cloud Cuckoo Lander: Turned Nico into a cornstalk, for one.
- Serious Business: Woe betide anyone who doesn't consider agriculture as important as he does.
KymopoleiaGoddess of sea storms. A daughter of Poseidon, and Percy's half-sister. Currently working for Gaea to get revenge on her parents and the mortals who have long since forgotten her. She has no Roman identity.
- Attention Whore: Joined Gaea to make the world remember her again.
- Cain and Abel: She joins the list of Percy's siblings who have tried to kill him.
- Dude, Where's My Respect?: Despite being an incredibly powerful goddess, she despairs over not getting the recognition she deserves.
- Heel–Face Turn: Jason wins her over by promising to erect shrines to her and the other minor gods at the Greek and Roman camps.
- In Universe Nickname: Jason and Percy just call her "Kym."
- The Mentor: She's the one who reveals to Jason and Percy how to defeat Gaea by reminding them of how Ouranos, a fellow primordial god and First Lord of the Sky, was ultimately defeated. She also warns Percy of his Fatal Flaw once again.
- Underwater Ruins: She makes her lair in the abandoned wreckage of her father's old palace.
- The Unfavorite: Her parents keep her away because they find her presence and powers disruptive.
- Unwanted Spouse: She was married off to Briares, whom she loathes.
AsclepiusGod of healers. Son of Apollo. Currently under lock and key beneath his temple, by order of Zeus himself.
- Back from the Dead: His specialty, and the reason he's locked away under his temple.
- Dressed to Heal: Your standard white coat and stethoscope.
- Sealed Good in a Can: He's entirely benevolent, but his ability to raise the dead enraged Hades enough that Zeus killed him. He was brought back as a god of medicine to appease Apollo, on the condition that he not perform any resurrections, and he's guarded by a Killer Robot modeled after his daughter Hygeia.
- Super Doc: Comes with the territory of being the god of healers.
- Try to Fit THAT on a Business Card!: If it's a medical skill that can be expressed as a string of letters, he's got it after his name. Leo loses count after twenty such acronyms.
Nike/VictoriaGoddess of victory and charioteer to Zeus.
- Bound and Gagged: After being successfully subdued by the Seven she's tied up and kept in the Argo II. The fact that her "gag" is a dirty sock and duct tape is given much emphasis.
- Competition Freak: Obsessed with victory in all its forms, which makes her case of the divine schizophrenia much harder to handle as she's so desperate to pick a winner between her two sides that she's much more volatile as a result. According to Percy and Annabeth this is a trait she shares with her children.
- Rock Monster: Her minions, the Nikai (or "Nikettes" as Leo christens them), are metal women.
- Winged Humanoid: Her preferred form has two large golden wings.
The goddess of the Earth and progenitor of the Titans and, by extension, the Olympians. Big Bad of the series.
- Affably Evil: She maintains a calm and polite air at all times, even when taunting heroes and all but outright saying she wants them dead.
- Big Bad: Of the series.
- The Chessmaster: Seems to have planned out or predicted an awful lot of characters' choices prior to the beginning of the story.
- Dishing Out Dirt: She is the Earth. Like in the original mythology, she does not have nature-based powers (this was the domain of Pan).
- The Dreaded: Everybody's scared of her. She is, after all, the earth.
- Eldritch Abomination: Seeing as her body is the entire planet.
- The End of the World as We Know It: The entire plot is about preventing Gaea from waking up, since this trope is what's going to happen if she does. And she can't be defeated, because her body is the planet Earth itself.
- Evil Matriarch: The mother of all the gods and monsters except for the most primordial of them.
- To Juno. Both are matriarchs who are generally disliked, but Juno wants to save the world while Gaea wants to destroy it.
- To Kronos, the previous Big Bad — she takes a more direct approach to manipulating the main players of the prophecy.
- Gaia's Vengeance: Although she's not directly taking it out on mortals, just the mythological creatures.
- Logical Weakness: Because she is the all-powerful Earth Mother, she's near-powerless when in the air.
- The Man Behind the Man: In the first book, behind her son Porphyrion.
- Manipulative Bastard: Definitely more keen on this tactic then Kronos was. Following the theme of family ties, she emotionally manipulates near everyone using loved ones (Piper, Percy, Leo, Hazel, even some gods). Frank is supposedly an exception, thanks to his convoluted legacy.
- Non-Action Big Bad: Because she's asleep, she pulls strings to get what she wants rather than directly doing things herself.
- Parental Favoritism: Very blatantly favored the giants over the Titans.
- Significant Birthdate: Invoked. She chooses August 1, the Feast of the Goddess of Hope, to begin the second Gigantomachy.
The Tartarus, a manifestation of the darkest part of the Underworld.
- Archnemesis Dad: To Damasen.
- Big Bad Duumvirate: Implied by his dialogue, and a logical conclusion given that he fathered the Giants with Gaea and is by far the most powerful of her affiliates.
- Body Horror: The entirety of Tartarus is his body. This is given nods throughout the book as Percy and Annabeth joke about how they're traversing across different parts of his anatomy.
- Dark Is Evil: Oh, you had better believe it!
- Disproportionate Retribution: Destroys Krios and Hyperion for the former describing him in an unflattering manner.
- The Dreaded: For very good reason. It takes a You Shall Not Pass by Bob and Damasen to slow him down long enough for Percy and Annabeth to escape. What, exactly, do you think happened to them afterwards?
- Eldritch Abomination: The realm of Tartarus is his body, and when he assumes a form to deal with them personally Percy and Annabeth have a hard time looking directly at him.
- Fighting a Shadow: The manifestation at the end of the book is simply a form he assumed to deal with the Heroes. His true form is the locale of Tartarus.
- Genius Loci: Tartarus' body is pretty much the Greek version of Hell.
- Kick the Dog: We probably weren't supposed to feel bad for Hyperion and Krios, but his reason for doing what he did to them just makes it callous.
- Knight of Cerebus: Twofold. Percy and Annabeth's trek across Tartarus (technically his body) is easily one of the darkest parts of the book, and things naturally get worse when he shows up in person.
- Mighty Glacier: Is slow but immensely powerful, due to never having taken on a humanoid form before.
- Offing the Offspring: Presumably did this to Damasen and Bob.
- Reality Ensues: He assumes an incredibly powerful humanoid form to crush Percy and Annabeth...and is barely able to walk, since he's a Genius Loci and has never done it before.
- Unskilled, but Strong: Thankfully, for all his power, he's clearly unused to combat in a corporeal form, a weakness the heroes are able to exploit. Justified, though, as he'd never summoned a physical manifestation of himself before this point, and was essentially taking his baby steps.
- Womb Level: The realm of Tartatus is his body.
- Arch-Enemy: Each one was designed to destroy a specific god.
- Back for the Finale: Come back regenerated and just as ready to destroy the demigods as ever in The Blood of Olympus. Of course, now that Reyna and Nico manage to unite the warring camps and cure the gods' schizophrenia, they are disposed of fairly easily.
- Eviler Than Thou: The gods and Titans are not saints and it is sometimes hard to see a difference between them. However, everyone agrees the giants are worse than both. Being children of the Greek version of Hell it is to be expected.
- Evil Knockoff: Of the Olympians
- Final Boss: In the first three books, quests to defeat the giants drive much of the plot — Porphyrion for the first, Alyconeus for the second, and Enceladus for the third. While not an official quest, Hazel's battle with Clytius fulfills this role for the fourth. And, of course, the fifth book deals with all of them.
- Gaia's Vengeance: They are it.
- Implacable Man: Their primary strength. They lack the vast magic possessed by the gods, but are designed to keep coming no matter what thanks to only being able to be killed by a god and demigod working together.
- Our Giants Are Bigger: The average giant or giant-sized monsters are around 10-12 feet tall. These giants are around 20 feet or more.
- Pride: A flaw shared by all of them and according to Nemesis they have more pride than the Olympians or Titans which is saying something. Each one thinks they are invincible in battle and can surely defeat the Olympians despite having lost before and individual giants being defeated by individual demigods. This causes them to severely underestimate their enemies leading to one humiliating defeat after another.
PorphyrionThe most powerful of the giants and their king. Deigned to be a direct counter to Zeus including power.
- Arch-Enemy: To Zeus.
- Authority Equals Asskicking: When at full strength.
- Blade on a Stick: His main weapon
- Curb-Stomp Battle: In the last book, He is on the receiving end of one at the hands of Zeus and Jason. Zeus nearly kills him with his Master bolt before Jason blows him off a cliff and Zeus uses another lighting blast to reduce him from ash. His own spear is sliced in half and he fails to mount any sort of defense or offense.
- The Dragon: To Gaea.
- Hair Decorations: Like most Giants. His "decorations" of choice are weapons (implied to be those of past enemies).
- Large and in Charge: Described as the tallest of the giants and the most built physically.
- Orcus on His Throne: Is resurrected in the first book only to do nothing over the next four while the heroes steadily advance toward him. Any actual planning or action is taken by Gaea.
AlcyoneusCounterpart to Pluto and the eldest of the Giants.
- Arch-Enemy: To Hades. Also to Hazel, seeing as she was the one who resurrected him.
- The Dragon: To Gaea, spanning the time period from the forties to Porphyrion's rise.
- The Heavy: Of The Son of Neptune.
- Made of Indestructium: Except if he's out of his homeland Alaska.
- Too Dumb to Live: As pointed out by Frank — when you're unkillable as long as you stay in the boundaries of the state of Alaska, you really shouldn't hang out in the part of the state that's only 10 miles wide.Frank: "Welcome to Canada, idiot."
EnceladusCounterpart to Athena.
- Evil Genius: The most intelligent of the giants and the tactician among them, but given how stupid some of his fellow giants are this isn't saying much.
- Flunky Boss: He's aided in his fight against Jason, Piper, and Leo by several Earthborn.
- Hair Decorations: He has bones braided into his hair.
- I Have Your Wife: Takes Tristan McLean hostage to force Piper's allegiance.
PolybotesCounterpart to Poseidon.
- Arch-Enemy: To Poseidon.
- The Brute: Powerful for sure, but clearly not the most cunning of the giants.
- Curb-Stomp Battle: In the last book, Both gives and receives one. He fights Percy in the water and his poison instantly takes Percy out, but is on the receiving end of one from Jason and Kymopoleia. And he only won the Percy battle because Percy intentionally swam into the poison because he felt he deserved to be punished for prior actions.
- Hair Decorations: He has live basilisks slithering in his hair.
- Informed Ability: Supposed to be the anti-Poseidon, and his mere presence left Percy in a shivering pile the first time he saw the giant. Percy proceeded to open up a can of whoopass on him when they encountered one another during the last battle, and Polybotes became the first giant to lose against a demigod in single combat (okay technically a god was there). Some anti-Poseidon.
- Paper Tiger: All of the giants vastly over-exaggerate themselves one way or the other, but Polybotes is the worst. Despite his frighting appearance and and status as the anti-Poseidon he is stymied by minor goddesses defeated relatively easily in single-combat with demigods. Especially hilarious in the second time it was underwater, which should have been his domain, against a child of the sky.
- Poisonous Person: His very touch turns water to poison.
- Prongs of Poseidon: Simultaneously of the sea, gladiator, and evil varieties.
ClytiusCounterpart to Hecate. Incinerated by Hecate. With the liberation of the Doors of Death from Gaea's control, he is currently the only destroyed member of the Giants.
- Anti-Magic: His Shroud of Darkness neutralizes the mist.
- Arch-Enemy: To Hecate.
- Black Cloak: One made out of smoke because, you know, Evil Wears Black.
- Energy Absorption: Since his Arch-Enemy is the goddess of magic, Clytius was designed to absorb all her magic attacks.
- Evil Sounds Deep: Described as sounding like a bass guitar.
- Hair Decorations: An aversion among giants; he has no special decorations. The only unusual thing is that the braids appear to be made of smoke.
- Kill It with Fire: The one way to defeat him is with magical fire.
- People Puppets: Controls Annabeth, Percy and Leo (and even corpses in the tombs of the Necromanteion) and uses their mouths to speak for him.
- Super Smoke: Controls smoke that absorbs all Mist and magic. It also is used to steal people's voices and drain their life force.
- The Quiet One: Out of all the Giants, Clytius rarely speaks.
- Voice for the Voiceless: Doesn't use his own mouth, rather he steals people's vocal cords and communicates using their mouths.
Otis & EphialtesCounterparts to Dionysus.
- Berserk Button: Exploited by Percy during his fight with Otis. Insulting ballet enrages him so that he makes stupid mistakes.
- Butt Monkey: Poor Otis owns this trope.
- The Dark Chick: The smallest and least threatening of the Giants seen thus far.
- Fan Disservice: Otis' form-fitting tutu.
- Hair Decorations: Gold and silver coins, and, at one point, fireworks.
- Identical Twin ID Tag: Ephialtes has purple hair; Otis's is green.
- Jerkass: Ephialtes.
- Real Men Wear Pink: Otis is fond of ballet and wears a tutu during the fight with Percy and Jason. Everybody else, Ephialtes included, finds this revolting.
- Sensitive Guy and Manly Man: With Otis as the sensitive one and Ephialtes as the Manly Man.
- Those Two Bad Guys: Always seen together and are characterized by their interactions with one another.
OrionCounterpart to Artemis and Apollo. In the original mythology, Orion, while sometimes depicted as a giant, did not participate in the Gigantomachy.
- Egomaniac Hunter: A curse by Apollo turned him into one in ancient times and upon his return from Tartarus he has become one to women.
- Face–Heel Turn: Originally sided with the gods against the giants and fell in love with his target.
- He-Man Woman Hater: Originally loved Artemis, but being rejected by her, cursed by Apollo, and sent down to Tartarus caused him to make an about face and hunt any "strong" women with a focus on Artemis' Hunters and the Amazons.
- Hunting the Most Dangerous Game: Strong women, specifically.
- Straw Misogynist: Is he ever. He despises strong women, and wooed Artemis partly so he could "tame" her.
- Trauma Conga Line: What caused him to join his fellow giants despite originally siding with the gods. First he was blinded for flirting (well, that's all he claims it was) with a mortal princess, given new eyes, joined the Hunters of Artemis (the only male) only to fall in love with Artemis and be rejected, cursed by Apollo who feared Artemis might grow weak in her vows of maidenhood, cursed to hunt down every beast of the earth till his own mother, Gaea had to send a giant scorpion to kill him, and finally sent down to Tartarus.
- You Can't Fight Fate: Tried to fight his destiny and fell in love with the goddess he was supposed to destroy. Being rejected, cursed, and finally cast down into Tartarus for his troubles caused him to accept his fate and fight the gods.
MimasGiant counterpart to Hephaestus. Resides in the Temple of Fear.
- Drop the Hammer: Carries a giant sledgehammer.
- Walking Techbane: Specifically invoked, as he was made to counter the god of technology. Around him, "maps are misread, devices break, data is lost, and the finest minds turn to mush" (which is why Annabeth has such a hard time with him).
PeriboiaPorphyrion's daughter and princess of the Giants. Counterpart to Aphrodite.
- The Smurfette Principle: The only female Giant we see, and also the only one not explicitly a child of Gaea.
HyperionTitan of Light and Lord of the East. Recurring character from Percy Jackson and the Olympians.
- And I Must Scream: Gets his essence sucked into Tartarus' maw along with Krios when the the latter speaks ill of him.
- Asshole Victim: Sure his fate was horrific, but he spent most of his screen-time before that point mocking Bob, leaving the audience little sympathy.
- Demoted to Extra: Not that he had much of a role in the original series, but there he was The Dragon who fought alongside Kronos and dueled Percy while killing all manner of demigods, nature spirits, and Hunters. Here, he doesn't even get to fight before Tartarus offs him.
- Jerkass: Mocked Bob at multiple points about his amnesia and generally acted like a spoiled brat.
- How the Mighty Have Fallen: To think he was The Dragon to Kronos in the previous series.
- Light Is Not Good: The Titan of the East, which can be interpreted as The Titan of Sunrise.
KriosTitan of the South and Lord of the Stars and Constellations. Defeated by Jason during the Roman attack on Mount Othrys, he currently resides in Tartarus, safeguarding The Doors of Death with Hyperion.
- And I Must Scream: For his careless (though accurate) description of Tartarus, the Dark God shreds him and Hyperion with an energy blast and consumes their essence.
- Asshole Victim: Not as badly one as Hyperion, but he did talk about wanting to kill Jason before getting blasted by Tartarus.
- BFS: Just like his brother Koios.
- Butt Monkey: Seriously, he got vaporized by Tartarus just for making one little insult about him. He also gets the least amount of respect of all the Titans.
- Dark Is Evil: Wears dark armor and Butt Monkey he may be, but he's still a Titan, and he expressed interest in getting to fight Jason for killing him back during the battle of Mount Orthys.
- The Eeyore: He's got some serious self-esteem issues compared to his brothers
- Green-Eyed Monster: Shown to be quite jealous of the more proactive Titans, Hyperion in particular.
- Ineffectual Sympathetic Villain: Considering his words and actions in the previous series along with his dialogue here, you can't help but feel at least a little bad for him when Tartarus blows him up.
- Jerkass: Less so than Hyperion, but he didn't exactly shower Bob with hugs when he showed up.
- Too Dumb to Live: Insulting Tartarus was a bad, bad idea.
KoiosTitan of Foresight and Lord of the North. Also the grandfather of Artemis and Apollo.
- Affably Evil: Of all of Bob's (Iapetus's) brothers, he's the only who greets him with a smile and genuinely acts brotherly, even expressing interest on getting revenge on Hades for reducing Bob to a mere janitor.
- BFS: His sword is the size of a surfboard.
- Boisterous Bruiser: He's as big and bulky as most Titans, and he's quite the affable guy...at least to his family. Percy notes that he has Apollo's (his grandson's) smile.
- Even Evil Has Loved Ones: He's the only one of Iapetus's (Bob's) family to seemingly care about him post-amnesia. Also, it's offhandedly mentioned, but he did express desire at having his daughter Leto, the mother of Artemis and Apollo, join them to take revenge on Zeus, apparently due to how Zeus treated her after they were born.
- Four-Temperament Ensemble: Sanguine.
- An Ice Person: As the Titan Lord of the North, he held the same position Boreas now does and thus is implied to hold similar powers.
- Icy Blue Eyes: Described as being as blue-white as a glacier and just as cold. Percy also admits they're a lot like his granddaughter Artemis's eyes.
- Sole Survivor: Of the four Titans (including Bob) that were seen in Tartarus, he's the only one whose death wasn't confirmed.
- The Starscream: He suggests that while it might be the giants who destroy Olympus this time, when Gaia awakes it will her favored children (the Titans) who will rule It's unknown exactly how much truth is in this statement though.
- What Happened to the Mouse?: It's unknown exactly what happened to him after the Doors of Death were sealed. As he wasn't there when Tartarus manifested and thus avoided Hyperion and Krio's fate, nor was he anywhere in sight during Bob and Damasen's Heroic Sacrifice, it can at least be assumed he survived likely with his daughter Leto. Whether he escaped Tartarus is another matter though...
MedeaPrincess of Colchis, department store manager.
- Charm Person: She has the power of charmspeaking.
MidasThe legendary king with the golden touch. Didn't learn his lesson after all.
- Affably Evil: Midas acts friendly to his guests while trying to turn them into gold.
- Arson, Murder, and Jaywalking: Midas forces demigods that find him to choose between being turned to gold or being murdered by his son, he works for Gaea, and runs a gold selling scam.
- Taken for Granite: Midas's power to turn people into gold.
- In-Series Nickname: His name is short for "Lityerses."
PhineasA blind man with the gift of prophecy brought back to life by Gaea. He gets killed by poison in a bet between him and Percy when Gaea decides to spare Percy rather than him.
- Animal Nemesis: He hates harpies.
- You Have Outlived Your Usefulness: He still had some, just not as much as Percy.
EidolonsMalevolent spirits with the ability to possess mortals, demigods, monsters, and machines.
- And I Must Scream: The three we see in The Mark of Athena end up forever fused to the remains of several completely trashed Automatons. Yeah, payback's a...
- Demonic Possession: Duh.
- Supernatural Gold Eyes: The telltale sign of eidolon possession.
ChrysaorThe Golden Warrior. Son of Posiden and Medusa, brother of Pegasus and half-brother of Percy.
- Attention Whore: He became a pirate for the attention since his brother got all the attention.
- Badass: He beat Percy in a sword fight, who compared him to Ares.
- Irony: He wants a bigger legend but the lack of information about him is what makes him so dangerous.
- Screw This, I'm Outta Here!: His crew when Percy bluffed Mr. D was coming.
- Wake-Up Call Boss: He is the only character in the series that can defeat Percy when he's at the top of his game in a straight fight.
- “I excel at pulling strings! I’m a spider!”
- All Webbed Up: As a giant spider, this is part of her powers.
- Arch-Enemy: She hates Athena.
- Back for the Dead: She shows up in person for literally about half a second in The House of Hades, trying to kill Annabeth, only to get killed by Percy.
- Body Horror: Her entire lower half is that of a black widow spider. She's very bitter about that.
- Enigmatic Minion: Shown to be complicit with Ephialtes and Otis, but the extent of her servitude to Gaea is never really explored. At any rate, she seems much more caught up in her own agenda.
- Fatal Flaw: Like Annabeth, hers is Pride.
PasiphaëWife of Minos and mother of the Minotaur.
- Broken Bird: Punished for her husband's crimes, and is bitter that Minos gets to be a judge of the Underworld despite how horrible of a human being he was.
- Disney Villain Death: And I Must Scream If not something worse.
- Interspecies Romance: She was cursed to fall in love with her husband's prize bull.
- Nice Job Fixing It, Villain: Resurrecting the Labyrinth.
- Small Role, Big Impact: Resurrects Daedalus's Labyrinth in her twenty-odd page appearance, inadverently providing the heroes with a way to get the Arthena Parthenos back to Camp Half-Blood.
ScironSon of Poseidon and bandit extraordinaire.
- Fearsome Foot: Tells Hazel and Jason that they have to clean his feet to let him go. Neither of them are happy about it, because his feet are absolutely disgusting, but also because as soon as you bend down, he kicks you right off the cliff.
Michael VarusSon of Janos and a former praetor of New Rome who infamously lost the legion's standard in Alaska.
- Ambition Is Evil: Described as being ambitious and prideful. He led the legion to Rome in a quest for glory, which resulted in a massacre.
- Meaningful Name: "Varus" means "crooked" in Latin, although the name most likely is a reference to the historic Publius Quinctilius Varus, who is most well known for losing three legions when ambushed.
- Our Ghosts Are Different: Can apparently hold their own in combat.
LycaonThe first werewolf.
- Back for the Finale: Reappears in the last book as a servant of Orion, out to get Reyna and Nico.
- Our Werewolves Are Different: Can turn into a full wolf, among other things, and shares the infamous weakness to silver — he is hurt by the silver arrows of the Hunters. Argentum (who is made of silver) can harm his wolves, but Aurum (gold) cannot.
- Wolf Man: The very first.
OthersCharacters not directly affiliated with any of the other groups, but still play roles in the story.
Other Mythological Creatures
The Hunters of ArtemisMortals, demigods, nymphs, or other young women sworn to Artemis. They join the goddess on her hunts and are blessed with agelessness and divine hunting prowess so long as they remain perpetual maidens. They are currently led by Thalia Grace.
- The Ageless: They appear as young as they did when they took the oath.
- Amazon Brigade: All-female and all-badass. The Blood of Olympus sees a team-up between them and the other Amazon Brigade of the series, the Amazons.
- Does Not Like Men: Forsworn to forsake men forever. Most of them actively avoid interaction for fear of losing their divine sponsorship.
- Great White Hunter: Blessed with divine ranged capabilities and Improbable Aiming Skills.
- Mauve Shirt: Phoebe, supporting Hunter since the first series and mentioned as the best tracker and healer (likely due to her age), is unceremoniously offed by Orion's attack in The Blood of Olympus.
- Power Glows: Said to have a silver aura.
- Really 700 Years Old: The more senior members have been around for years and years and don't look out of their teens. Phoebe in particular is mentioned to have been there during the first fiasco with Orion, three or four thousand years ago.
- The Straight and Arrow Path: Use traditional hunting gear (eg. bows and arrows) in a story set in the 2010s.
The AmazonsA tribe of female warriors who worship war gods (like Ares, Athena, or Bellona). Unlike the Hunters of Artemis, they are allowed to have relationships and children with men — as long as those men are fine with being treated like second-class citizens. They are lead by Hylla.
- Amazon Brigade: Trope Namer.
- Back for the Dead: The Amazons return in The Blood of Olympus and are near-massacred by Orion.
- Cavalry Betrayal: In The Son of Neptune they arrive rather late to the Gaea's forces vs. Camp Jupiter battle... and turn out to be helping the demigods instead.
- Challenging the Chief: Any Amazon can obtain leadership by challenging and killing the Queen.
- Does Not Like Men: Subverted. The Amazons like men perfectly fine — they just like men knowing their place even more.
- Hypocrite: They boast that the world would be a more peaceful place with women in charge despite being a Proud Warrior Race.
- Lady Land: Amazon HQ. The Amazons' boyfriends are basically servants.
- Mauve Shirt: Kinzie, friend to Hylla and supporting Amazon in The Son of Neptune, is killed by Orion in The Blood of Olympus.
- Product Placement: The Amazons own Amazon.com, and some read on their Kindles when they ought to be on guard duty.
- Straw Feminist: They keep their boyfriends in orange jumpsuits and collars.
EchoA nymph who fell in love with Narcissus, and is doomed to always echo what she previously hears.
- Hopeless Suitor: For Narcissus. She loves him, but he only loves himself.
- Ironic Echo: Literally. She's been cursed by Hera for gossiping a lot to echo whatever she hears last.
- Love Martyr: She's spending her second chance at life still trying to help Narcissus break from his curse. He pays no attention to her, and because of her curse she's almost invisible to everyone else.
- Love Redeems: She's trying to do this for Narcissus.
- Visible Invisibility: Part of her punishment at the hands of the gods, she always mirrors any background she walks in front of, causing her to appear camouflaged and invisible. She shows her true face to Leo for a moment, and Leo remarks that she was actually kind of pretty, although the memory of her face was already slipping away.
- What Beautiful Eyes!: When she kisses Leo, he marvels at her blue eyes.
LamiaA peppy old woman who booked Claymore's event in Keeseville, New York. She's mostly an annoyance to Claymore. Only shows up in The Demigod Diaries. She turns out to be a monster in disguise and the half-sister of Alabaster through Hecate. She's been tracking Alabaster with the intent of murdering him on Gaea's orders, forcing him to move from town to town and constantly keep up magic barriers to hold her off. Thanks to being brought back from Tartarus by Gaea, she can't die, making it difficult for Alabaster to get rid of her for good.
- And I Must Scream: As of the end of Son of Magic, Alabaster knows a spell that will keep her essence from departing to Tartarus, meaning that if he destroys her she will be stuck as a sentient pile of dust for all eternity. Hecate thinks the threat of this should be enough to keep her at bay.
- Bitch in Sheep's Clothing: Hinted at later on, when after acting like an enthusiastic and sweet, if rather irritating, grandmotherly old lady to Claymore, she calls him to demand he hand over the card about Alabaster's address to her for no discerned reason. Comes to fruition when she shows her true nature as a monster who works for Gaea.
- Cain and Abel: The Cain to Alabaster's Abel.
- Disproportionate Retribution: Yes, Hera killing her children was wrong, but crafting a magic to let monsters find demigods everywhere, and then keeping it running, racking up demigod casualties, for three thousand plus years, is way overreacting.
- Even Evil Has Loved Ones: She wants to bring back her children, which Gaea promised to do for her. For her, if killing Alabaster means having them back, then so be it.
- Freudian Excuse: In the past, when she was a Libyan queen, she was courted by Zeus and had two children she loved. When Hera found out about her relationship with Zeus, she murdered Lamia's children, and in front of her, no less. Needless to say, Lamia didn't take it well.
- Genki Girl: An elderly version, but she's quite enthusiastic and full of praise for Claymore after he's finished with the event. Subverted, however, when she's revealed to be a monster.
- Greater Scope Villain: She's the one who granted monsters the power to detect demigods, meaning that she's probably got more demigod deaths on her hands than any other villain.
- Mama Bear: A twisted variant. She loves her children dearly and will bring them back to life at any cost, even if it means working for Gaea and murdering people.
- Small Role, Big Impact: She only appears in a short story in The Demigod Diaries, but what she did before both Percy Jackson and the Olympians and The Heroes of Olympus even started — namely, giving monsters the power to sense demigods and track them down by their scent — is a big factor in the story.
- She probably has more demigod deaths on her hands than any other character in the story.
- Would Hurt a Child: Really, really wants to murder Alabaster.
Rachel Elizabeth Dare
- "We have to work together to defeat Gaea."
- Brick Joke: The blue hairbrush she used to thwack Kronos in the face with in the previous series makes a reappearance in The House of Hades when Rachel and Grover meet with the Romans.
- Brought Down to Normal: The power of prophecy still isn't working by the end of The Blood of Olympus, leaving her without her powers.
- Fainting Seer: When the Oracle possesses her.
- Foil: To Octavian.
- Full Name Ultimatum: In The House of Hades, she addresses Reyna by her full name.
- Demoted to Extra: Has a far less important role in The Heroes of Olympus than in the previous series, besides getting some mentions, an appearance in the first book, and an appearance in a dream (alongside Grover) in the fourth.
- Out of Focus: Doesn't appear in the second and third books, although she returns in the fourth.
Beryl GraceJason and Thalia's mother, a beautiful Hollywood starlet.
- '80s Hair: Her description in the previous series includes that she had a "poofy hairdo".
- Abusive Parents: Attracting the king of the gods (twice) had a negative effect on her ego, and eventually she turned to alcohol. This led to many arguments with Thalia. She's not above offering her son as a peace offering for an angry goddess, either.
- The Alcoholic: She turned to drink later in life, which caused her rift with her daughter.
- Love Makes You Crazy: Her inability to get over Zeus and her own pride turned her into a mania, a spirit of insanity, who haunts her son in the last book.
- Missing Mom: To Thalia and Jason.
- No Name Given: The only one of the Seven's mortal parents to not be named. She's finally named by the last book.
- Posthumous Character: She's dead by the story proper.
- White-Dwarf Starlet: Described in the previous series to be an "eighties starlet with a poofy hairdo."
Tristan McLeanPiper's father, who works as a movie star.
- Fake Nationality: In-universe, he never plays a Native American in any movie he's in, despite being Cherokee.
- Hostage Situation: Gaea kidnaps him so that Piper will do what she wants. It doesn't work.
- Mind Wipe: Piper gives him a drink that erases his memory of the whole ordeal, even if it helped the two of them grow closer.
- Parental Neglect: While he's presented positively, he tends to leave a bad taste in the mouth once one remembers that Piper rarely gets to spend time with him, and that time is usually under a minute.
- Parents as People: His difficulties juggling his job and his daughter, as well as his relative weak will compared to other characters, are given extensive focus.
- Parents in Distress: He's held hostage in The Lost Hero to blackmail his daughter.
- Window Love: With Piper, after he loses his memory.
- Weak-Willed: Somewhat. He can't handle the existence of the Mist, which Aphrodite cites as her reason for staying away.
Marie LevesqueHazel's deceased mother, who worked as a fortune teller in New Orleans.
- Abusive Parents: Became this when possessed by Gaea.
- Be Careful What You Wish For: She was very poor and couldn't escape poverty. When the spell she cast summoned Pluto, they dated, and after Hazel was born, Pluto promised her anything she wanted. She asked for all the riches under the earth, and Hazel got the power to summon and control jewels and precious metals... but everything she summons is cursed, unless she or Pluto touches it. Everything Marie sold brought horrible fates to those who bought them, and she ended up just as poor.
- Demonic Possession: She often gets possessed by Gaea.
- Dying as Yourself: Only came back to her normal self before dying with Hazel on the sinking island.
- Expy: Of Marie Laveau, the Voodoo Queen of New Orleans, although she lived significantly later (though considering the rumors that Laveau somehow became immortal, one has to wonder...)
- Fortune Teller: She was a con artist, although Hecate says she had magic of her own.
- Missing Mom: To Hazel.
- My God, What Have I Done?: Just before Alcyoneus is about to rise, she realizes what her selfishness caused and is willing to give up her life to save Hazel. However, Hazel doesn't let this happen and instead dies with her to delay Alcyoneus's rise.
- Posthumous Character
Grandmother ZhangFrank's grandmother, who was his guardian after his mother's death.
- Animorphism: Turns into a vulture after the family mansion burns down.
Emily ZhangFrank's deceased mother, who died in the war against Afghanistan.
- Action Mom: Not only did she serve on the front lines in Afghanistan, she could also turn into animals!
- Animorphism: The Zhang gift.
- Deceased Parents Are the Best: Frank remembers her fondly.
- Doting Parent: When she was alive.
- Heroic Sacrifice: She died in the war to save her fellow soldiers.
- Lady of War: Described as being very calm and graceful, but an excellent fighter.
- Love Will Lead You Back: An inversion — after never seeing Mars for years, it's implied that she went to war in Afghanistan because she thought she'd meet him there. Whether this was true or not, we don't know, sadly.
- Mama Bear: Figuratively and literally. She turned into a bear to protect her son from one.
- Missing Mom: To Frank.
- Posthumous Character: Deceased by the story proper.
- The Squadette: Was one of the first female Canadians to serve on the frontlines during the war.
Esperanza ValdezLeo's deceased mother.
- Deceased Parents Are the Best: When Leo's not angsting about killing her with his fire powers, he remembers her fondly.
- Doting Parent: As much as she could, when she was alive.
- Meaningful Name: Her name means "hope".
- Missing Mom: To Leo.
- Plucky Girl: Described as such in the backstory. Despite the discrimination and hardships she faced she was always determined, optimistic, and kind, as well as a doting parent to Leo.
- Posthumous Character: Deceased by the story proper.
- Spicy Latina: Averted. She was described as being very warm and friendly, as well as satisfied with her living conditions as long as she had Leo.
- Wrench Wench: Very talented with machines, which, perhaps unsurprisingly, attracted the attention of Hephaestus.
JaneTristan McLean's secretary, and the one who minds Piper when he's busy.
- Beleaguered Assistant: Looking after the rebellious kleptomaniac Piper can't be easy.
- Prim and Proper Bun: She's described as wearing her hair up in a bun at all times.
- Resentful Guardian: To Piper.
- Weak-Willed: According to Medea, and it's true, seeing how easily Medea was able to order her around.
SammyHazel's almost-boyfriend from her time in New Orleans. His surname just happens to be Valdez, and he's Leo's great-grandfather.
- Class Clown: Seemed to be one during Hazel's schooling years.
- First Love: For Hazel.
- Generation Xerox: His great-grandson Leo looks exactly like him.
- The One That Got Away: To Hazel. According to Gaea, had she lived Hazel would have grown up to marry him.
- Only Friend: To Hazel.
- Only One Name: He's only known as Sammy, nothing more. Until The Mark of Athena, where it turns out his surname is "Valdez", same as Leo's.
- Satellite Love Interest: Not much is known about him as a character other than being Hazel's First Love and Leo's great-grandfather.
- Twofer Token Minority: Mexican-American, so he jokes that the St. Agnes School for Colored Children and Indians should have given him a double scholarship.
- What Could Have Been: In-Universe: If Hazel had stayed in New Orleans, she would have grown up to marry Sammy.
Julian Ramirez-ArellanoFather to Reyna and Hylla and lover to Bellona, a soldier who went off to fight in Iraq.
- Love Makes You Crazy: His love for Bellona coupled with his PTSD turned him into a borderline abusive, overprotective father to Reyna and Hylla. By the time of his death he'd degenerated into a mania.
- Shell-Shocked Veteran: Was never quite the same after his turn in Iraq.
Dr. Howard ClaymoreA mortal living in Keeseville, New York. A scholar who gives lectures when he's not writing and finds his life and everything he knew turned on its head after meeting Alabaster Torrington. Shows up only in a short story, Son of Magic, at the end of The Demigod Diaries.
- Awesomeness by Analysis: He can understand Latin, which gives him an edge when Lamia uses Latin spell incantations, as he can make pretty good guesses what's about to happen. His observations of how quickly Lamia can pull herself together after being wounded also works to his advantage, or seems to. See Unwitting Pawn.
- Badass Normal: Fights Lamia with just a 9mm pistol and Good Old Fisticuffs.
- Determinator: Started with no advantages in life, but still was able to get a PhD and become a successful author, and has no intention of letting gods or monsters get the better of him.
- Heroic Sacrifice: Attacks Lamia one final time to give Alabaster time to escape.
- Properly Paranoid: His outer fence is well away from his house, which has a state-of-the-art security system, and a gun in each room. And he knows how to use them, too.
- Spirit Advisor: After his death, Hecate makes him one for Alabaster.
- Unfazed Everyman: Thought he's only just become aware of the existence of gods and monsters, he just considers then another problem to be solved through his usual, logical method.
- Unwitting Pawn: After defeating Lamia, he goes off to find Alabaster, unaware that Lamia let him win and then followed him to the demigod's safe house.
- Would Hit a Girl: Holds his own against Lamia and shows no qualms about beating her up while she keeps trying to regenerate.
- You Remind Me of X: Hecate tells him that he reminds her and Alabaster of Alabaster's father.