In The Titans curse , Nico is ten years old and enjoys playing with his mythomagic cards that none of the truly seem to understand , and , as revealed in The blood of Olympus he was obsessed with pirates even before that . He is clueless and very inquisitive : he is curious and questioning and likes Percy a lot like a big brother ( though it is later revealed in The house of Hades that he has secret romantic feelings for him ) , and begins annoying Percy with his ceaseless questions , especially when he asks is Annabeth Chase his girlfriend , which 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 Huntress of Artemis . When she goes on a quest , Nico makes Percy promise to protect her. After her death , he develops a long - lasting grudge towards Percy for letting her die . Once he realizes he is a son of Hades , he casts away his childhood interests and runs off on his own .
In The Battle of labyrinth , Nico becomes grim and solitary , and defiantly a considerably more powerful character , saying that "only the dead respect me.......and only out of fear " . His attitude change may of happened partly because of Bianca's death and partly because of Minos's manipulation . He believes that he will never be excepted by the living , and does not belong at Camp Half Blood , much like how his father Hades feels out of place in Olympus . Nico is also shown to be somewhat vengeful , as he wanted revenge for Bianca's death , something he blamed Percy for . However Nico 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 same book , he is shown to be very naive and gullible , being able to believe that Minos was actually helping him bring Bianca back from the dead . Nico cares much about his sister and the constant attempts to bring her back show that he will not give up without trying . Nico is shown to be very loyal to the Olympians , as he could have easily joined Kronos and the Titans , but chose to fight on the Olympian's side .
In The last Olympian , he is quite sincere in wanting to help Percy with the prophecy and the war . However , Nico can be somewhat untrustworthy at times . This is shown when he tricked Percy into coming to the Underworld so he can gain answers about his mother , but Nico wasn't planning on Percy becoming imprisoned . By standing up to both Kronos and Hades , he is shown to be very brave and bold . In fact , the only time Nico himself is ever shown to be terrified , is in the House of Hades , when he was forced to face Cupid implying that Nico's greatest fear is exposing his homosexuality . He likes being on his own , not really wanting help from anyone . He keeps to himself a lot and is pretty secretive , which causes plenty of problems throughout the series . Nico wants to help Percy , and was very miserable at the thought that Percy did not trust him after his dad tricked him as well , by the end they were back to a brotherly relationship .
While he tries hard not to show it , Nico is plagued by incredible internal pain , , mainly due to him being unable to come to terms with not "belonging" in the twenty-first century ( due to the time he spent in the Lotus Casino ), not being accepted by other demigods as as on of Hades , and , worst of all his homosexuality ( which he is desperate to keep a secret ) . Some of his fears about not being accepted due to being gay , most likely come from growing up in the 1940s , where homosexuality was not accepted . At some point during his horrifying journey through Tatarus , Nico encounters the goddess of misery Akhlys , much sorrow and pain the son of Hades carried , claiming that there was little more that she could do to him . When Reyna shares her strength with Nico in The Blood of Olympus , she is horrified at how much pain and raw anguish she felt inside the son of Hades , even a portion of it being greater than what she had felt from even her entire legion during the battle against the giant Polybotes . When accidentally learns about Nico's homosexuality , she , much to Nico's surprise and relief , doesn't judge him , and still accepts him as a friend just as he is , without hesitation . Reyna's acceptance was what most likely gave Nico the courage to finally come out to a very surprised Percy and Annabeth , but he admits to being over his formerly strong crush on Percy , and is now genuinely happy for Percy and Annabeth . Hence , Nico is finally ready to become more sociable and more open about himself and his feeling to others , no longer nearly so insecure about his homosexuality. Nico , apparently , also has tremendous , virtually indomitable willpower , since he was able to survive in Tatarus on his own , while seeing the place in all of it's ineffable horror for the entire time that he spent there . Percy , who found even a few moments of seeing it maddening ,marveled how Nico had managed to survive with his sanity .
Nico is later proven wrong in the belief he will not be accepted by the living . After the war with Kronos is over , all the demigods of Camp Half Blood welcome Nico cheerfully : as Percy puts it : "Hey , show up with an army of undead warriors to save the day , and suddenly you're everyone's best friend " . This helps lift Hades curse from the Oracle . Sadly , however Nico's popularity only lasted a few weeks , after which most campers did whatever they could to avoid the son of Hades and forgot he was at camp . However , when Nico mentions his plans to leave for good , due to his lack of acceptance , Will Solace gets upset and tells him that they are actually many people at camp who are his friends or would like to be , but it is Nico who pushes himself away . Will also states that the camp did not reject him as he thought . This indicates that Nico may have misinterpreted the camper's reactions to him , or exaggerated it in his own mind , due to his fears of non-acceptance . After Gaia is defeated , when Reyna tells the two camps about Nico's part in saving both of them , and gives him a big hug , the crowd of demigods roard with approval , indicating that thanks to Reyna, both Camp half blood and Camp Jupiter have finally come to truly accept the son of Hades . As a result , Nico tries to give Camp half blood another try , finally seeing that he is accepted .
In spite of Nico's pretending not to know Percy in the Son of Neptune , he spoke very highly of him to Hazel , telling her that he is dangerous to his enemies and a valuable ally to his friends . Nico's relationship with Percy also shows how much he's grown and matured throughout the series . Nico is very caring to Hazel Levesque , his half sister , and tries to help her as much as he can . His helping her sort of parallels with how Percy helped him in several cases. This shows that he loves his family , even his half siblings . Unfortunately, after returning from Tatarus in The mark of Athena , Nico is very different . He turns more inward and withdrawn , with his eyes becoming somewhat glassy like something in him broke permanently. Percy compares him to pictures of prisoners of war , which he notes Nico kind of was . Hazel states in The house of Hades that Nico has become more reclusive and morose , preferring to stay on the top of the ships mast , in solitude . Nico becomes much more easily agreed , defensive and to make creepy and humorless smiles . Nico , however , has happily smiled on two occasions : in The Last Olympian , right after he helps Hades defeat Kronos's army and gains his fathers respect , and in The house of Hades , after he and Frank defeat Gaia's monsters at the Necromenteion In The blood of Olympus , Nico notes that his facial muscles hurt when he smiles , since he isn't use to making that expression often . Even though Nico seems to dislike being touched , he is shown to be very affectionate towards Hazel , having kissed her on the cheek several times . However by the end of The blood of Olympus , Nico begins to change , and doesn't seem to mind when Reyna and Jason embrace him .
Nico can be extremely dangerous since he is a son of the big three . He is very unpredictable , and due to his sisters death can be somewhat mentally unstable as demonstrated in The Battle of Labyrinth . He has a short temper , just like Percy and Thalia . When Jason causes him to loose his temper in The house of Hades , Nico's fury was so intense , that it even scared Jason , who felt that a furious Nico was "More than he could handle " . However , the greatest and most volcanic demonstration of Nico's fury happened in The blood of Olympus , when he faced the psychopathic Bryce Lawrence . A furious Nico , in one horrible cry , unleashes a flood of pain and anger on Bryce , Reyna , and Coach Hedge , with the temperature around Nico dropping to freezing ( turning the ground around him white with frost ) Bryce's zombies instantly disintegrating , and a terrified Bryce himself turned into a mindless ghost.