The House of Hades

The House of Hades is the fourth book in The Heroes of Olympus series. It was released on October 8th, 2013. The book takes place where The Mark of Athena left off.

Development
The title, The House of Hades, refers to the location of the mortal side of the Doors of Death, the House of Hades, an underground temple in Epirus. There will be a few scenes in the book that are in Tartarus. On June 18th, 2013, the audiobook for The Son of Sobek became available and included a preview of the first chapter. In the preview, it is confirmed that Hazel Levesque will be one of the narrators. Later Rick Riordan read a small exert from the book, revealing Annabeth Chase as another one of the narrators. However during an interview, Rick Riordan revealed that all seven characters would be narrating the book from their own points-of-view.

Synopsis
At the conclusion of The Mark of Athena, Annabeth and Percy tumble into a pit leading straight to the Underworld. The other five demigods have to put aside their grief and follow Percy's instructions to find the mortal side of the Doors of Death. If they can fight their way through the Gaea's forces, and Percy and Annabeth can survive the House of Hades, then the Seven will be able to seal the Doors both sides and prevent the giants from raising Gaea. But, Leo wonders, if the Doors are sealed, how will Percy and Annabeth be able to escape? They have no choice. If the demigods don't succeed, Gaea's armies will never die. They have no time. In about a month, the Romans will march on Camp Half-Blood. The stakes are higher than ever in this adventure that dives into the depths of Tartarus.



Plot
The Argo II has been relentlessly attacked for two days by rock gods called numina montanum in Latin (or ourae in Greek). Leo Valdez defends the ship by firing celestial bronze canons at them. Once his attacks fail, they fly away from the Apennine Mountains. Leo wants to wake Frank Zhang, Piper McLean, and Jason up, but Hazel vetoes his idea because barely any of them have been able to sleep due to the attacks. Hazel blames the attacks on the fact that earth spirits do not like children of Hades/Pluto, as they are children of the Underworld. The trio throw around suggestions on how to get over the mountains. Hazel prays to her dad to give her a sign of help and in the distance she spots Arion. Hazel then tells Leo to get close enough to the ground where she can talk to Arion. She meets Hecate, the goddess of magic. Hecate tells her that her mother, Marie Levesque was gifted in magic. She tells Hazel that she will also learn sorcery, or the ability to manipulate the Mist, in order to save Percy and Annabeth. Hecate shows Hazel 3 doorways, telling her to choose her path. The western doorway shows Roman and Greek demigods fighting one another on a hillside under a pine tree. Hazel was riding Arion trying to stop the fight. The eastern doorway shows the Argo II above the Apennines, but the ship is badly damaged. The northern doorway shows Leo, Frank and herself severely injured. Percy and Annabeth lay unmoving. Hecate then tells her to choose one of these doorway or go backward. Hazel picks the middle doorway, but tells Hecate that she is not choosing any of her choices, and that she will save Percy and Annabeth, stop Gaea and the Giants, and prevent the Greek-Roman war at the same time, with the others. She then returns to the Argo with Arion.

Meanwhile, Annabeth and Percy are still falling into Tartarus. Annabeth tells Percy, as her supposed last words, "I love you". Annabeth then sees the bottom and a river flowing below, so she tells Percy to try and control the water from it to survive. They succeed in cushioning their fall, but the river is Cocytus, the River of Lamentation. The pair feel all of the sorrow and misery of bitter souls. The spirits from the river urge them to succumb, but Annabeth tells Percy to fight back, telling him of their dream future in New Rome. They barely survive, and collapse onto the shore.

The two then realize that the shore is made out of glass shards, and the air of poison. Percy and Annabeth are badly intoxicated. Annabeth remembers that the River of Fire in Tartarus has healing properties. They find the river, and drink from it, temporarily healing themselves. Suddenly, Arachne appears and tries to attack, but Percy kills her with Riptide.

Percy and Annabeth are then attacked by Empousai, including Kelli, though they are unexpectedly rescued by Iapetus, who is still convinced that his name is actually Bob. Iapetus/Bob then joins them on their trek back to the world. Along the way, they battle more monstrous creatures of Tartarus and encounter a helpful Giant, Damasen, who had been created to oppose Ares but was not warlike and so was banished to Tartarus.

As the Argo II approaches Bologna, it is boarded by two mischievous monkey-like dwarfs, Akmon and Passalos, the Cercopes, who steal Leo's Archimedes sphere, tool belt and Piper's knife before fleeing. Leo and Jason pursue them into the city, before cornering them in their lair hidden inside Bologna's landmark the Two Towers, and forcing them to return the stolen items, along with an astrolabe and an old book which turns out to belong to the agricultural god Triptolemus, who lives in Venice. Leo then allows the dwarfs to keep the rest of their loot, on the condition that they would harass the Roman army and delay them from reaching Camp Half-Blood.

The crew of the Argo II then proceed to Venice to return the stolen book to Triptolemus and ask for his aid. Frank, Hazel and Nico, who was born in Venice and still speaks Italian, venture into the city and find it infested with anteater-like herbivorous monsters called katoblepones which were inadvertently brought into Venice from Egypt many centuries ago. The trio soon discover that the creatures exhale poison, but not before the poison overcomes Hazel. Nico and Frank decide that finding Triptolemus and asking him to heal Hazel was their best option. They find Triptolemus initially unwilling to help because he is a son of Demeter, whose daughter, Triptolemus' sister Persephone, was abducted and forced into marriage by Nico and Hazel's father; when Nico protests, he is turned into a plant. Frank, however, soon persuades him; seeing that the chariot Triptolemus once used to travel throughout the world teaching agriculture is disabled due to having only one of the two snakes it needs to fly, Frank cleanses Venice of the katoblepones, leaving only one, which he gets his father Mars to turn into a python. Frank then gives it to Triptolemus to replace the missing snake on his chariot. Triptolemus, pleased, turns Nico back to human, heals Hazel, and tells them how to survive an ordeal they must face to enter the House of Hades: they will be immunized from poison they must drink before going in by eating barley cakes.

Proceeding south down the Adriatic toward Greece, the crew of the Argo II is waylaid on the coast of Croatia by a bandit called Sciron who is assisted by a giant predatory sea turtle and kills his victims by making them wash his feet and then kicking them off a cliff into the ocean for the turtle to devour. Hazel uses the Mist to trick Sciron into kicking Hazel inland instead of off the cliff. She then subsequently tricks Sciron into being kicked off the cliff and gobbled up by the turtle himself. Pluto then appears to her and tells her that the Doors of Death are at the lowest level of the Necromanteion, the temple of Hades in Epirus where they are going, and will be guarded by Pasiphaë, a Cretan sorceress who was the wife of Minos and mother of the Minotaur.

Jason has a dream in which he learns that Annabeth has managed to send a message intended for Reyna to Rachel Dare at Camp Half-Blood from Tartarus; Rachel, accompanied by Grover Underwood, delivers the message to Reyna, who is with Octavian and the other centurions of New Rome atop a Manhattan skyscraper. In order to stop the war between Camp Jupiter and Camp Half-Blood, Reyna must personally deliver the Athena Parthenos to Camp Half-Blood. Reyna then mounts her pegasus, Scipio, and heads for Europe, dismissing the protests of Octavian. Upon awakening, Jason directs Leo to change course for Split, Croatia, the site of the palace and tomb of the Roman Emperor Diocletian, a personal hero of Jason and Reyna, whose scepter is said to be able to control the spirits of dead Roman soldiers who worshiped the gods of Olympus.

At Diocletian's tomb, Jason and Nico are confronted by Favonius, the Roman god of the west wind, and by Cupid, the Roman god of love, who are the guardians of Diocletian's scepter; Cupid extorts a confession from Nico as the price of giving him and Jason the scepter: Nico had fled Camp Half-Blood after Bianca's death not just because he felt rejected by the other campers as the son of Hades, and not just Percy had let him down by failing to keep Bianca safe--he had romantic feelings for Percy, which he could not deal with.

Jason has seen in a psychic dream that Reyna is on her way, and, assuming correctly that she will take advantage of being in the region by visiting Diocletian's tomb, leaves a note for her near the tomb directing her on where to go from there.

As the Argo II continues on toward Greece, the weather becomes unseasonably and mysteriously cool and cloudy, and then Khione, the goddess of snow, who Jason, Piper and Leo confronted in The Lost Hero, attacks the ship and sends Leo to Ogygia, the island home of Calypso, in Malta. Calypso, who has become bitter over being trapped on the island with no means of escape and no permanent romantic relationship, resists Leo's presence, but slowly warms up to him, and when he finally leaves the island, he is determined to free her from her exile and vows on the River Styx to return to her.

In Tartarus, Percy and Annabeth meet Akhlys, the goddess of misery and poison. She enshrouds them in death mist and betrays them. A fight ensues.

Jason has had daily audiences with Auster, the Roman god of the south wind, in connection with the Seven being able to proceed on their way to Epirus. Auster is naturally capricious and indolent but yet seems increasingly disinclined to cooperate with Jason. Meanwhile, Jason has been thinking that he misses Camp Half-Blood and that he never really fit in at the more formal, traditional, even hidebound Camp Jupiter, and that he may have been changed irrevocably by his time at Camp Half-Blood. When Auster finally agrees to meet with him, he indicates that Jason is not committed to one course, Greek or Roman, personally; Jason's heart now lies with Camp Half-Blood, and Auster forces him to commit to it. Once Jason has done so, Auster changes to his Greek counterpart Notus and decides to send The Seven on their way. They then proceed to Valletta, Malta, where they find the Argo II fully repaired and moored out in the harbor so that they will be sure to notice it, and Leo at a cafe, pensive because of his encounter with Calypso; and they continue on to Epirus.

Arriving at the Necromanteion, Jason, Hazel, Frank, Leo, and Piper descend into the ruins, and eat barley cakes to protect themselves against the toxic potion they must drink in order to enter the temple, as per Triptolemus' instructions. Earthquakes strike the caverns as they walk through them, and monsters assail them. Nico uses the Scepter of Diocletian to summon ghostly Roman soldiers, but they will not obey Jason, as they sense that he is no longer Roman, and some, but not all, obey Frank, who may not command the entire force, as he is only a centurion. Jason resigns his praetorship and gives it to Frank, who then takes command of the undead soldiers and defeats the monsters.

When Percy and Annabeth arrive at the Doors of Death, which is a magic elevator from Tartarus to the world similar to the elevator in the Empire State Building in New York providing access to Olympus, they find Gaea's Giants and other monsters boarding the elevator. Bob tells Percy and Annabeth how they can escape: when the doors open, they have twelve minutes to enter the elevator, making sure no one else enters with them, before the doors close. The elevator ride up to the world takes twelve minutes, and then the doors must open again quickly or whoever or whatever is inside will vanish and be destroyed. Percy and Annabeth have twelve minutes to leave the elevator before the doors close again, and they are guarded at the upper end by Pasiphaë and Clytius, the Giant created to oppose Hecate. The Doors of Death normally move around unpredictably, but the elevator doors are held open with magical chains on the upper end, fixing them so that the elevator travels only between Tartarus and a cavern at the Necromanteion's lowest level. In order to close the Doors of Death, and free them so that they resume their normal wandering behavior, these chains must be cut.

Bob volunteers to drive the Titans Hyperion and Coeus, who are guarding the elevator, away from the doors and hold the elevator open so that Percy and Annabeth may escape Tartarus. Percy protests, since he knows that this will mean Bob's death, but Bob insists. They are then confronted by Tartarus, the god of the pit, who tries to stop them and is confronted by Damasen; together, Bob and Damasen come to their aid and hold off Tartarus while Annabeth and Percy escape the underworld.

Meanwhile, in the Necromanteion, the rest of the heroes confront Pasiphae and Clytius. Pasiphae informs them that she is regenerating the Labyrinth, which was destroyed when Daedalus died in The Battle of the Labyrinth, and intends to use it for her own purposes, to aid Gaea. As the elevator arrives with Annabeth and Percy inside, Clytius and Pasiphae attempt to kill them by preventing the elevator doors from opening, but Leo opens the door with a well-thrown screwdriver aimed at the button. Hazel uses the Mist to get Percy and Annabeth out of the elevator and then to drop Pasiphae back into Tartarus through a pit which suddenly opens underneath her feet, then cuts the chains on the elevator doors with her sword, thereby closing the Doors of Death, which vanish. The heroes then set upon Clytius, and Hecate, who has appeared to watch the battle, cremates him alive with her torches to finish him off, as Bacchus had Ephialtes and Otus in the Colosseum of Rome in The Mark of Athena. Before disappearing, she warns them to leave quickly, as the ruins have become unstable; Nico cannot shadow-transport all eight of them, but they manage to do it with the aid of Hazel, who has never previously shadow-traveled before. They reappear on a hillside outside the temple, with the Argo II hovering overhead, as they left it. Hedge lands the ship, and they see Reyna is with them. She is without Scipio, who she was forced to euthanize after he collapsed immediately upon landing on the deck; he had been mortally wounded in an attack by a gryphon the night before.

The ten of them share a meal on the hillside, and it is decided that Nico will transport Reyna and the statue back to Camp Half-Blood through shadow travel, along with Coach Hedge, who wishes to be with his wife the wind spirit Mellie, who is pregnant with their child and was caught at Camp Half-Blood by the war while on vacation from her job as Piper's father's personal assistant. The rest of the heroes continue on toward Athens on the Argo II, and Percy, remembering that Bob missed seeing the stars and had asked Percy to say hello for him to them, looks up at the night sky and says to the stars, "Bob says hello."

Chapter List
There are no chapter titles. Each chapter has a name of one of the main characters and is written in Roman Numerals. There are 78 chapters. Unlike in the previous books in the Heroes of Olympus series which alternates third person narration among three or four characters every four chapters, this book features third person narration of seven characters in no proper order.

Trivia

 * On page 535, Hazel incorrectly claims that Gaea forced her and her mother to raise Porphyrion. It should have been Alcyoneus.
 * On page 252, Rachel refers to Apollo as Octavian's father, rather than his ancestor. Strangely, Octavian doesn't correct her.
 * This is the only book so far where both Titans and Gigantes are encountered.