Achelous a potamus, or river god
Aegis Thalia Grace’s terror-inducing shield
Aeolus god of all winds
Akhlys Greek goddess of misery; goddess of poisons; controller of the Death Mist; daughter of Chaos and Night
Alcyoneus the eldest of the giants born to Gaea, destined to fight Pluto
Alodai twin giants who attempted to storm Mount Olympus by piling three Greek mountains on top of each other. Ares tried to stop them, but he was defeated and imprisoned in a bronze urn, until Hermes rescued him. Artemis later brought about the giants’ destruction when she raced between them in the form of a deer. They both took aim with their spears, but missed and instead struck each other.
Aphrodite the Greek goddess of love and beauty. She was married to Hephaestus, but she loved Ares, the god of war. Roman form: Venus
Aquilo Roman god of the North Wind. Greek form: Boreas
Arachne a weaver who claimed to have skills superior to Athena’s. This angered the goddess, who destroyed Arachne’s tapestry and loom. Arachne hung herself, and Athena brought her back to life as a spider.
arai female spirits of curses; wrinkled hags with batlike wings, brass talons, and glowing red eyes; daughters of Nyx (Night)
Archimedes a Greek mathematician, physicist, engineer, inventor, and astronomer who lived between 287–212 BCE and is regarded as one of the leading scientists in classical antiquity; he discovered how to determine the volume of a sphere
Ares the Greek god of war; the son of Zeus and Hera, and half brother to Athena. Roman form: Mars
argentum silver; the name of one of Reyna’s two metallic greyhounds that can detect lies
Argo II the fantastical ship built by Leo, which can both sail and fly and has Festus the bronze dragon as its figurehead. The ship was named after the Argo, the vessel used by a band of Greek heroes who accompanied Jason on his quest to find the Golden Fleece.
Argonauts in Greek mythology, a band of heroes who sailed with Jason on the Argo, in search of the Golden Fleece
Ariadne a daughter of Minos who helped Theseus escape from the Labyrinth
Arion an incredibly fast magical horse that runs wild and free, but occasionally answers Hazel’s summons; his favorite snack is gold nuggets
astrolabe an instrument used to navigate based on the position of planets and stars
Athena the Greek goddess of wisdom. Roman form: Minerva
Athena Parthenos a giant statue of Athena, the most famous Greek statue of all time
augury a sign of something coming, an omen; the practice of divining the future
aurum gold; the name of one of Reyna’s two metallic greyhounds that can detect lies
Auster Roman god of the South Wind. Greek form: Notus
Bacchus the Roman god of wine and revelry. Greek form: Dionysus
ballista (ballistae, pl.) a Roman missile siege weapon that launched a large projectile at a distant target (see also scorpion ballista)
barracks the living quarters of Roman soldiers
Bellona a Roman goddess of war
Boreads Calais and Zethes, sons of Boreas, god of the North Wind
Boreas god of the North Wind. Roman form: Aquilo
braccae Latin for trousers
Bunker Nine a hidden workshop Leo discovered at Camp Half-Blood, filled with tools and weapons. It is at least two hundred years old and was used during the Demigod Civil War.
Cadmus a demigod whom Ares turned into a snake when Cadmus killed his dragon son
Calypso the goddess nymph of the mythical island of Ogygia; a daughter of the Titan Atlas. She detained the hero Odysseus for many years.
Camp Half-Blood the training ground for Greek demigods, located on Long Island, New York
Camp Jupiter the training ground for Roman demigods, located between the Oakland Hills and the Berkeley Hills, in California
catapult a military machine used to hurl objects
Celestial bronze a rare metal deadly to monsters
centaur a race of creatures that is half human, half horse
centurion an officer of the Roman army
Ceres the Roman goddess of agriculture. Greek form: Demeter
charmspeak a blessing bestowed by Aphrodite on her children that enables them to persuade others with their voice
chiton a Greek garment; a sleeveless piece of linen or wool secured at the shoulders by brooches and at the waist by a belt
Circe a Greek goddess of magic
Clytius a giant created by Gaea to absorb and defeat all of Hecate’s magic
Cocytus the River of Lamentation in Tartarus, made of pure misery
cohort one of ten divisions in a Roman legion; a group of soldiers
Colosseum an elliptical amphitheater in the center of Rome, Italy. Capable of seating fifty thousand spectators, the Colosseum was used for gladiatorial contests and public spectacles, such as mock sea battles, animal hunts, executions, reenactments of famous battles, and dramas.
cornucopia a large horn-shaped container overflowing with edibles or wealth in some form. The cornucopia was created when Heracles (Roman: Hercules) wrestled with the river god Achelous and wrenched off one of his horns.
Cupid Roman god of love. Greek form: Eros
Cyclops a member of a primordial race of giants (Cyclopes, pl.), each with a single eye in the middle of his or her forehead
Daedalus in Greek mythology, a skilled craftsman who created the Labyrinth on Crete in which the Minotaur (part man, part bull) was kept
Damasen giant son of Tartarus and Gaea; created to oppose Ares; condemned to Tartarus for slaying a drakon that was ravaging the land
Demeter the Greek goddess of agriculture; a daughter of the Titans Rhea and Kronos. Roman form: Ceres
denarius (denarii, pl.) the most common coin in the Roman currency system
Diocletian the last great pagan emperor, and the first to retire peacefully; a demigod (son of Jupiter). According to legend, his scepter could raise a ghost army.
Diomedes a principal Greek hero in the Trojan War
Dionysus the Greek god of wine and revelry; a son of Zeus. Roman form: Bacchus
Doors of Death the doorway to the House of Hades, located in Tartarus. The Doors have two sides—one in the mortal world and one in the Underworld.
drachma the silver coin of Ancient Greece
drakon a gigantic yellow and green serpent-like monster, with frills around its neck, reptilian eyes, and huge talons; it spits poison
dryads tree nymphs
Earthborn Gegenees in Greek; monsters that wear only a loincloth and have six arms
eidolons possessing spirits
Elysium the section of the Underworld where those who are blessed by the gods are sent to rest in eternal peace after death
empousa a vampire with fangs, claws, a bronze left leg, a donkey right leg, hair made of fire, and skin as white as bone. Empousai [pl.] have the ability to manipulate the Mist, change shape, and charmspeak in order to attract their mortal victims.
Epirus a region presently in northwestern Greece and southern Albania
Eris goddess of strife
Eros Greek god of love. Roman form: Cupid
faun a Roman forest god, part goat and part man. Greek form: satyr
Favonius Roman god of the West Wind. Greek form: Zephyros
Fields of Asphodel the section of the Underworld where people who lived neither a good nor a bad life are sent after death
Fields of Punishment the section of the Underworld where people who were evil during their lives are sent after death to face eternal punishment for their crimes
Furies Roman goddesses of vengeance; usually characterized as three sisters—Alecto, Tisiphone, and Megaera; the children of Gaia and Uranus. They reside in the Underworld, tormenting evildoers and sinners. Greek form: the Erinyes
Gaea the Greek earth goddess; mother of Titans, giants, Cyclopes, and other monsters. Roman form: Terra
Geras god of old age
Geryon a monster with three bodies that was slain by Heracles/Hercules
gladius a short sword
Graecus the word Romans used for Greek
greaves shin armor
Greek fire an incendiary weapon used in naval battles because it can continue burning in water
gris-gris In this New Orleans Voodoo practice named after the French word for gray (gris), special herbs and other ingredients are combined and put into a small red flannel bag that is worn or stored to restore the balance between the black and white aspects of a person’s life.
gryphon a creature with the forequarters (including talons) and wings of an eagle and the hindquarters of a lion
Hades the Greek god of death and riches. Roman form: Pluto
Hannibal a Carthaginian commander who lived between 247 and 183/182 BCE and is generally considered to be one of the greatest military strategists in history. One of his most famous achievements was marching an army, which included war elephants, from Iberia over the Pyrenees and the Alps into northern Italy.
harpy a winged female creature that snatches things
Hecate goddess of magic and crossroads; controls the Mist; daughter of Titans Perses and Asteria
Hemera goddess of day; daughter of Night
Hephaestus the Greek god of fire and crafts and of blacksmiths; the son of Zeus and Hera, and married to Aphrodite. Roman form: Vulcan
Hera the Greek goddess of marriage; Zeus’s wife and sister. Roman form: Juno
Heracles the son of Zeus and Alcmene; the strongest of all mortals. Roman form: Hercules
Hercules the son of Jupiter and Alcmene, who was born with great strength. Greek form: Heracles
Hermes Greek god of travelers; guide to spirits of the dead; god of communication. Roman form: Mercury
Hesiod a Greek poet who speculated that it would take nine days to fall to the bottom of Tartarus
Horatius a Roman general who single-handedly held off a horde of invaders, sacrificing himself on a bridge to keep the barbarians from crossing the Tiber River. By giving his fellow Romans time to finish their defenses, he saved the Republic.
House of Hades a place in the Underworld where Hades, the Greek god of death, and his wife, Persephone, rule over the souls of the departed; an old temple in Epirus in Greece
Hyperion one of the twelve Titans; Titan lord of the east
Hypnos Greek god of sleep. Roman form: Somnus
hypogeum the area under a coliseum that housed set pieces and machinery used for special effects
Iapetus one of the twelve Titans; lord of the west; his name means the Piercer. When Percy fought him in Hades’s realm, Iapetus fell into the River Lethe and lost his memory; Percy renamed him Bob.
ichor the golden fluid that is the blood of gods and immortals
Imperial gold a rare metal deadly to monsters, consecrated at the Pantheon; its existence was a closely guarded secret of the emperors
Janus Roman god of doorways, beginnings, and transitions; depicted as having two faces, because he looks to the future and to the past
Juno the Roman goddess of women, marriage, and fertility; sister and wife of Jupiter; mother of Mars. Greek form: Hera
Jupiter the Roman king of the gods; also called Jupiter Optimus Maximus (the best and the greatest). Greek form: Zeus
Kampê a monster with the upper body of a snake-haired woman and the lower body of a drakon; appointed by the Titan Kronos to guard the Cyclopes of Tartarus. Zeus slew her and freed the giants from their prison to aid him in his war against the Titans.
katobleps a cow monster whose name means “down-looker” (katoblepones, pl.). They were accidentally imported to Venice from Africa. They eat poisonous roots that grow by the canals and have a poisonous gaze and poisonous breath.
Katoptris Piper’s dagger
Kerkopes a pair of chimpanzee-like dwarfs who steal shiny things and create chaos
Khione the Greek goddess of snow; daughter of Boreas
Koios one of the twelve Titans; Titan lord of the north
Krios one of the twelve Titans; Titan lord of the south
Kronos the youngest of the twelve Titans; the son of Ouranos and Gaea; the father of Zeus. He killed his father at his mother’s bidding. Titan lord of fate, harvest, justice, and time. Roman form: Saturn
Labyrinth an underground maze originally built on the island of Crete by the craftsman Daedalus to hold the Minotaur (part man, part bull)
Laistrygonian giant a monstrous cannibal from the far north
Lar a house god, ancestral spirit (Lares, pl.)
legionnaire Roman soldier
lemures Roman term for angry ghosts
Leto daughter of the Titan Koios; mother of Artemis and Apollo with Zeus; goddess of motherhood
Lotus Hotel a casino in Las Vegas where Percy, Annabeth, and Grover lost valuable time during their quest after eating enchanted lotus blossoms
Mansion of Night Nyx’s palace
manticore a creature with a human head, a lion’s body, and a scorpion’s tail
Mars the Roman god of war; also called Mars Ultor. Patron of the empire; divine father of Romulus and Remus. Greek form: Ares
Medea a follower of Hecate and one of the great sorceresses of the ancient world
Mercury Roman messenger of the gods; god of trade, profit, and commerce. Greek form: Hermes
Minerva the Roman goddess of wisdom. Greek form: Athena
Minos king of Crete; son of Zeus; every year he made King Aegus pick seven boys and seven girls to be sent to the Labyrinth, where they would be eaten by the Minotaur. After his death he became a judge in the Underworld.
Minotaur a monster with the head of a bull on the body of a man
Mist a magic force that disguises things from mortals
Mount Tamalpais the site in the Bay Area (Northern California) where the Titans built a palace
naiads water nymphs
Necromanteion the Oracle of Death, or House of Hades in Greek; a multileveled temple where people went to consult with the dead
Neptune the Roman god of the sea. Greek form: Poseidon
New Rome a community near Camp Jupiter where demigods can live together in peace, without interference from mortals or monsters
Notus Greek god of the South Wind. Roman form: Auster
numina montanum Roman mountain god (montana, pl). Greek form: ourae
nymph a female nature deity who animates nature
nymphaeum a shrine to nymphs
Nyx goddess of night; one of the ancient, firstborn elemental gods
Odysseus legendary Greek king of Ithaca and the hero of Homer’s epic poem The Odyssey. Roman form: Ulysses
Ogygia the island home—and prison—of the nymph Calypso
ourae Greek for mountain god. Roman form: numina montanum
Ouranos father of the Titans
Pasiphaë the wife of Minos, cursed to fall in love with his prize bull and give birth to the Minotaur (part man, part bull); mistress of magical herbal arts
Pegasus in Greek mythology, a winged divine horse; sired by Poseidon, in his role as horse-god, and foaled by the Gorgon Medusa; the brother of Chrysaor
Periclymenus an Argonaut, the son of two demigods, and the grandson of Poseidon, who granted him the ability to change into various animals
peristyle entrance to an emperor’s private residence
Persephone the Greek queen of the Underworld; wife of Hades; daughter of Zeus and Demeter. Roman form: Proserpine
phalanx a compact body of heavily armed troops
Phlegethon the River of Fire that flows from Hades’s realm down into Tartarus; it keeps the wicked alive so they can endure the torments of the Fields of Punishment
pilum (pila, pl.) a javelin used by the Roman army
Pluto the Roman god of death and riches. Greek form: Hades
Polybotes the giant son of Gaea, the Earth Mother
Polyphemus the gigantic one-eyed son of Poseidon and Thoosa; one of the Cyclopes
Porphyrion the king of the giants in Greek and Roman mythology
Poseidon the Greek god of the sea; son of the Titans Kronos and Rhea, and brother of Zeus and Hades. Roman form: Neptune
praetor an elected Roman magistrate and commander of the army
Proserpine Roman queen of the Underworld. Greek form: Persephone
Psyche a young mortal woman who fell in love with Eros and was forced by his mother, Aphrodite, to earn her way back to him
quoits a game in which players toss hoops at a stake
Riptide the name of Percy Jackson’s sword; Anaklusmos in Greek
River Acheron the fifth river of the Underworld; the river of pain; the ultimate punishment for the souls of the damned
River Lethe one of several rivers in the Underworld; drinking from it will make someone forget his identity
Romulus and Remus the twin sons of Mars and the priestess Rhea Silvia. They were thrown into the River Tiber by their human father, Amulius, and were rescued and raised by a she-wolf. Upon reaching adulthood, they founded Rome.
Saturn the Roman god of agriculture; the son of Uranus and Gaea, and the father of Jupiter. Greek form: Kronos
satyr a Greek forest god, part goat and part man. Roman equivalent: faun
Scipio Reyna’s pegasus
Sciron an infamous robber who ambushed passersby and forced them to wash his feet as a toll. When they knelt, he kicked his victims into the sea, where they were eaten by a giant turtle.
scorpion ballista a Roman missile siege weapon that launches a large projectile at a distant target
Senatus Populusque Romanus (SPQR) meaning “The Senate and People of Rome,” it refers to the government of the Roman Republic and is used as an official emblem of Rome
shadow-travel a form of transportation that allows creatures of the Underworld and children of Hades to travel to any desired place on earth or in the Underworld, although it makes the user extremely fatigued
Sibylline Books a collection of prophecies in rhyme written in Greek. Tarquinius Superbus, a king of Rome, bought them from a prophetess named Sibyl and consulted them in times of great danger.
spatha a heavy sword used by Roman cavalry
Spes goddess of hope; the Feast of Spes, the Day of Hope, falls on August 1
stela (stelae, pl.) an inscribed stone used as a monument
Stygian iron a magical metal, forged in the River Styx, capable of absorbing the very essence of monsters and injuring mortals, gods, Titans, and giants. It has a significant effect on ghosts and creatures from the Underworld.
Tantalus In Greek mythology, this king was such a good friend of the gods that he was allowed to dine at their table—until he spilled their secrets on earth. He was sent to the Underworld, where his curse was to be stuck in a pool of water under a fruit tree, but never to be able to drink or eat.
Tartarus husband of Gaea; spirit of the abyss; father of the giants
telkhine a sea demon with flippers instead of hands, and a dog’s head
Tempest Jason’s friend; a storm spirit in the form of a horse
Terminus the Roman god of boundaries and landmarks
Terra the Roman goddess of the Earth. Greek form: Gaea
Thanatos the Greek god of death; servant of Hades. Roman form: Letus
Theseus a king of Athens who was known for many exploits, including killing the Minotaur
Three Fates In Greek mythology, even before there were gods, there were the Fates: Clotho, who spins the thread of life; Lachesis, the measurer, who determines how long a life will be; and Atropos, who cuts the thread of life with her shears.
Tiber River the third-longest river in Italy. Rome was founded on its banks. In Ancient Rome, executed criminals were thrown into the river.
Tiberius was emperor of Rome from 14–37 CE. He was one of Rome’s greatest generals, but he came to be remembered as a reclusive and somber ruler who never really wanted to be emperor.
Titans a race of powerful Greek deities, descendants of Gaea and Uranus, who ruled during the Golden Age and were overthrown by a race of younger gods, the Olympians
Triptolemus god of farming; he aided Demeter when she was searching for her daughter, Persephone, who was kidnapped by Hades
trireme an Ancient Greek or Roman warship, having three tiers of oars on each side
Trojan Horse a tale from the Trojan War about a huge wooden horse that the Greeks built and left near Troy with a select force of men inside. After the Trojans pulled the horse into their city as a victory trophy, the Greeks emerged at night, let the rest of their army into Troy, and destroyed it, decisively ending the war.
Trojan War In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband, Menelaus, king of Sparta.
venti air spirits
Venus the Roman goddess of love and beauty. She was married to Vulcan, but she loved Mars, the god of war. Greek form: Aphrodite
Vulcan the Roman god of fire and crafts and of blacksmiths; the son of Jupiter and Juno, and married to Venus. Greek form: Hephaestus
Wolf House where Percy Jackson was trained as a Roman demigod by Lupa
Zephyros Greek god of the West Wind. Roman form: Favonius
Zeus Greek god of the sky and king of the gods. Roman form: Jupiter