Nico and Bianca were born before World War II, so technically Hades never broke the oath he took to never have any half-blood children. They both lived in Washington DC. When Nico and Bianca were young, their mother died when Zeus struck the hotel they were staying at with lightning while trying to kill Nico and Bianca. Both were brought to the Lotus Hotel by the FuryAlecto, who was disguised as a lawyer in order to protect them. Alecto was also instructed by Hades to bathe them in the River Lethe to wipe their memories. After their mother died, the Oracle, showing up shortly after the destruction of the hotel, was cursed by an angry Hades to never have the Oracle 's soul rest and to be locked in that body, even after it died, until he and his children became accepted in Olympus. This resulted in her being the mummy of the Oracle at Camp Half-Blood until the end of the second Titan War.
After what they thought was a month in the Lotus Hotel and Casino, which was actually approximately 70 years, they were taken out by Alecto who was disguised as the same lawyer who carried them in. Hades did this because he wanted one of them to be the child in the prophecy and not the "idiot" son of Poseidon, referring to Percy.
Nico first appears with his sister, in a military school called Westover Hall , in Bar Harbor, Maine. Bianca and Nico were almost kidnapped by a manticore named Dr. Thorn. Thalia, Grover, Percy, and Annabeth attempt to save them, but it is the Hunters of Artemis who come to the rescue. The siblings were sought out by Grover Underwood, who believed them to be two very powerful unknown half-bloods. Nico is about ten, and seems to be very interested in Mythomagic, a card game about Greek mythology, that bares somewhat of a resemblance to Yu-Gi-Oh or Pokemon. But when 12 year-old Bianca accepts Artemis' proposal to become a Hunter, Nico gets angry at her for abandoning him. Percy finds Nico eavesdropping on Bianca and Zoë, and Nico successfully convinces Percy to promise to keep his sister safe. He doesn't appear again until the end of the book, where Percy explains to him that Bianca died to save the others on the quest. He immediately turns on Percy, telling him he hates him, and reminding him of the promise he made to keep Bianca safe. Percy tries to comfort him, and Nico claims he can sense her soul being judged. When the last four Skeleton Warriors appear in the camp, Nico tells them to "Go away!" and they are swallowed by a fissure in the ground that Nico creates by accident. Nico is last seen running into the woods at night. Percy then realizes that Nico is a son of Hades after finding the god statue that Bianca told Percy to give to Nico after she died. The statue was of Hades, Lord of the dead.
Nico is first seen through the Iris message that Bianca sent to Percy. He has honed his powers as the son of Hades with help from the ghost of King Minos, who had been training him. He tried to summon Bianca's ghost many times, but failed. Frustrated, he seeks to make a deal with his father by trading "a soul for a soul." Percy thinks that Nico is after him, but Nico is after somebody else.
Nico decides to find the soul of someone who cheated death and trade it for Bianca's. Later, he meets Percy, Annabeth, Tyson, and Grover at the Triple G Ranch. He'd entered Triple G Ranch to discuss finding the soul he needed with Geryon. Angered, he threatens them, but is stopped by Geryon. He still blames Percy for Bianca's death, and tells him so. He is then tied by Geryon to be sold to the TitanArmy. When Percy offers a deal to Geryon to save him, Nico shouts that he does not want to be saved by Percy.
Percy still saves Nico, and convinces him to try and summon Bianca's spirit again. However, Bianca tells Nico not to be angry at Percy or hold grudges, because that is the fatal flaw of the children of Hades. She says to stop blaming Percy because it is really she that Nico is angry at for abandoning him. She also gives a warning aboutKronos sensing Nico, and then she disappears.
He stays at the Triple G Ranch while the others leave. Nico is tricked by Minos into going back into the maze to save Percy, but is captured by two dracanae of Kronos'. In the battle at Daedalus' workshop, Nico opens a fissure in the ground, sending Minos back to the underworld. He tells Percy that only the dead accept him, and they only do that out of fear.
He escapes with Percy, Annabeth, and Rachel, who have to go back into the Labyrinth to find Grover and Tyson. Along the way, they see Kronos (in the form of Luke), and Nico, in a desperate attempt to save everyone, shows his true powers, conjuring a wall of black stone making it known to Kronos that he is a son of Hades.
During a battle in the labyrinth, Nico summons undead warriors to fight. The effort nearly kills him, and he collapsed on the ground at the end of the battle. Percy finds him and helps him by giving him nectar. He releasesDaedalus's soul after that, who offers his soul for ransom, but Nico decides Bianca should stay where she is.
He feels out of place at Camp Half-Blood, and refuses to eat with the other demigods or join the singalong at the amphitheater. Nico summons Bianca's spirit one last time. He tells Percy that he will leave Camp Half-Blood because he feels that he doesn't belong there like his father doesn't belong on Olympus. Before he leaves, Percy gives him the small Hades statue that Bianca had given him before she died.
He appears again at the very end to Percy and offers a way to defeat Kronos, but is distracted by Percy's blue birthday cake (assuming he's probably never had a birthday party in his life), and Percy offers him some, and they both go inside, which leads into the next book.
Nico is one of the three demigods (along with Thalia and Percy, or all the known children of the Big Three) whom are summoned by his step-mother Persephone to find the Sword of Hades. His knowledge of the underworld and of its occupants within it help them complete their quest. He remains in the underworld afterward to discuss the oncoming war with his father. Before his friends leave, he reminds Percy of his idea to defeat the Titans.
Nico's theory to gain an edge over the Titans is to make Percy invincible by having him bathe in the River Styx, similar to the myth of Achilles. It is shown that after Bianca died, Hades feels he has no competent child, repeatedly mentioning that Bianca could do a better job at fulfilling their father's demands.
Nico is first seen in one of Percy's dreams where he is eavesdropping on a group of Titans. It is later confirmed that this was true. Percy sees him again while walking Mrs. O'Leary. Nico is with Juniper and Leneus, discussing Grover's disappearance. Nico, Percy, and Mrs. O'Leary then meet Mrs. Castellan on a disturbing visit by shadow-travel. Soon after, the three enter the Underworld, where Percy is trapped by Hades and rescued by Nico. Nico helps Percy bathe in the River Styx.
It is also revealed that the lawyer who removed the children from the Lotus Hotel and Casino was the lead Fury, Alecto, in disguise. Nico attempts to summon the ghost of his mother, but Bianca appears and tells him not to. He sees the scene of their mother's death in which Zeus blasted the building she, Hades, and the children were in to pieces. Hades, who realized what was happening too late, only managed to save the children Nico and Bianca. He then tells Alecto to wipe the children's memories of their mother's death.
By viewing this scene, Nico finds out who his mother is and is able to convince his father to help the campers in battle. He fights in the Battle of Manhattan with his father, the Lord of the Underworld. Together, they summon wave after wave of soldiers of the undead against Kronos's forces. Nico is last seen ordering undead workers to build the Hades cabin, made up of solid obsidian walls with a skull over the door. Torches blaze with burning green fire that will never extinguish.
Nico is mentioned in The Lost Hero to be searching for Percy along with Tyson, Grover and the Hunters of Artemis, but otherwise doesn't appear. It's to be assumed that he doesn't stay at Camp Half-Blood much, as Annabeth said he "sometimes" shows up.
In The Titan's Curse, Nico is ten years old and enjoys playing with his Mythomagic Cards that none of the others truly seem to understand. He is totally clueless and very inquisitive: he begins annoying Percy with his ceaseless questions, especially when he asks questions about Annabeth, which eventually makes Percy consider "stuffing him in a meat flavored sack and throwing him to the wolves." He is excited about finding out that he is a Demigod(immediate response: "Cool!"), and compares monsters to Mythomagic creatures. He feels abandoned when his sister, Bianca--who practically acts as his parent--becomes a Hunter of Artemis. When she goes on a quest, Nico makes Percy promise to protect her. After her death, he develops a long-lasting grudge toward Percy for letting her die. Once he realizes that he is a son of Hades, he casts away his childhood interests and runs off on his own.
He becomes more a dark and solitary character during The Battle of the Labyrinth, saying that "only the dead respect him... and only out of fear". He believes that he will never be accepted by the living, and does not belong at Camp Half-Blood, but forgives Percy after Bianca's ghost tells him that it wasn't his fault that she died. He also accepts the small figurine of Hades that Bianca wanted him to have.
In the fifth book, The Last Olympian, he brings Percy to his father to get information about his mother that proves to be the least his father can give, and his father ends up putting Percy in a dungeon. When Nico later comes to help Percy escape, Percy immediately pins him to the floor, holding his sword to his throat, and accuses Nico of betraying him. Nico reasons with him, and when Percy releases him, he helps Percy out of the Underworld prison cell anyway. As they escape, Nico puts skeleton guards to sleep by pointing at them, but this tires him and he collapses before making the remark, "With great power. . .comes great need to take a nap. Wake me up later." He instructs Percy on how to bathe in the River Styx. Even though he annoys Percy a lot (by this point in the book, he is no longer annoyingly inquisitive, and no longer annoys Percy), he is quite sincere in wanting to help him with the prophecy and the war.
Nico is later proven wrong in the belief he will not be accepted by the living. After the war is over, all the campers of Camp Half-Blood welcome Nico cheerfully: as Percy puts it,"If you come into battle with a hundred undead soldiers to save the day, you're everyone's friend."
He is said to have shaggy black hair, olive skin that has paled over the course of The Battle of the Labyrinth, brown eyes, and wears mostly black, (a pair of ripped black jeans, black shirt) sort of gothic clothing, and by the end of The Battle of the Labyrinth, a silver skull ring. When he shakes hands with Percy at the end of the Battle of Labyrinth, Percy says that Nico's hand is "cold as ice." He is also mentioned on several occasions wearing an aviator's jacket, most likely because he had distant relatives in WWII.
Nico di Angelo's fatal flaw is holding grudges, as Bianca's ghost tells him - which, in his case, can lead to not wanting help or asking to be saved in deadly situations because he doesn't like someone. Examples are his not wanting to be helped by Percy, even when Geryon was going to sell him to the Titans and not wanting to go back in the Labyrinth with them. Bianca shares this with him, as she also had the same fatal flaw in life, although this didn't lead to her death. Bianca also says that holding grudges is the fatal flaw of Hades' demigod children. In the fifth book, Nico tells his father that he (Hades) is holding a grudge that could end up killing the Olympians and the campers.
A Stygian ironsword. It is three feet long, and in the Last Olympian is described as being "black as a nightmare." It helps Nico to channel his power to control and summon the dead, and it can also drain souls to give the sword more power. Only Hades and his children can use Stygian Iron for their weapons.
Nico is one of the most powerful demigods ever seen. Like most demigods, Nico has ADHD and Dyslexia. As a son of Hades, Nico is himself an underworld deity. He is considerably more trained in using his powers than other children of the Big Three, such as Thalia and Percy.He has Necromancy,Umbrakinesis and Geokinesis. His confirmed powers include:
Divine authority and control over the Furies and the dead.
Geokinesis: Control of the earth, levitating rocks and making them deadly, black, and extremely sharp, the ability to create earth tremors, and open fissures in the earth. Can cause earth tremors so powerful, they can shatter the pillars of a mountain fortress.
The name Nico is the diminutive form of Nicolò, the Italian form of the Greek Nikolaos (Nicholas), meaning "victory of the people." It is most likely intended to evoke the prefix necro-, meaning dead. His surname is Italian for "of angels," alluding to his role as the Lord of the Dead's son.
The line "With great power. . .comes great need to take a nap." is a near obvious reference to one of Spider-Man's most famous line: "With great power, comes great responsibility", albeit a bit altered for comedic effect and to indicate that Nico's powers tire him greatly, prompting him to take naps every now and again to regain his strength, as he did at that moment in The Last Olympian.
Nico's birthday was never told in the books, but it has been said that Rick Riordan revealed it to be January 28th, 1924. It's said that Rick also revealed his birthday to be May 16th, 1924. It is unknown which one is the correct date.
Nico was turned into a dandelion for a short period of time by Persephone during a "family spat."
He does not like to be called "Bianca's little brother."
Nico has been to a New Orleans graveyard, it is unknown why he went though. Interestingly, this is one of the favorite hangouts of another death god (a.k.a. Anubis, the Egyptian god of funerals).
Nico blushes when a female touches him. Either when they do it show affection or appreciation (Shown when Juniper, Grover's girlfriend, touches his arm in The Last Olympian).