Imagine him aged up too!! Imagine him in his 20s, still going between the camps but in an official capacity, and though people may try to pin him down they never are able to. Sometimes he’s at camp Jupiter, sometimes camp half blood, sometimes he takes side quests upon himself and disappears for weeks at a time and no one knows if he’s at the other camp or in the underworld or randomly in the Philippines or something.
He is absolutely terrifying because he doesn’t try to hide the fact that he’s a son of hades. He uses his powers freely, openly, shadowtraveling from place to place, summoning zombies to run messages for him, turning transparent mid-fight as if he’s becoming a ghost himself, his enemies’ weapons sailing right through him.
He doesn’t really do quests anymore, but sometimes he’s summoned to help with other peoples quests. He has a special set of knowledge about all things underworld, all souls lost and damned, all creatures who might be looking for payback. Sometimes, he’s summoned to help with a quest that involves meeting with a god, and while the younger inexperienced demigods are shaking in their shoes, nico isn’t impressed by gods anymore. Sometimes, he helps with quests to the underworld, and while he’s there he bows respectfully to his father, kisses his step-mom on the cheek.
Once, he having an intense conversation with someone when a raging monster broke into camp, sending everyone into a panic. He ignored it at first, rolling his eyes, but when the monster tried to trample the table they were at he just narrowed his eyes and waved his hand, and tendrils of smoke rose up from the ground, surrounding the beast and pulling it straight down to tartarus. Nico continued on with his conversation, ignoring the interuption.
There are lots of rumors about Nico, the Son of Hades, the Ghost King. Some say that he wasn’t born normally, that he just emerged from the darkness. Some say that if he sits and has a long talk with you, that means you can sense that you’re about to die. Some say that he can hear your heart beat in your chest, smell your fear. They say hes killed thousands of monsters. There are rumors that he’s killed demigods too– in the Titan War, the Giant War, in combat practice, what have you. No one knows whats true, and he doesn’t speak about his life, so there’s no way to tell for sure.
They don’t know the long hours he spends with his friends– usually at night, alone in their cabins. They don’t know about the way he sleeps for 14 hours a night, the way he can never seem to get cold, the way he drinks nutrition shakes because he can’t seem to put on weight even though he’s really, really trying. They don’t know how the mortal side of him is just as prominent as the godly side– how he decorates his room in Hades’ palace for when he eventually dies, how he thinks about going back to school (he dropped out at 12, maybe younger?) but doesn’t see the point, how he reads ghost stories and gets ideas for new ways to scare monsters into submission. No one knows.