One of the first things Nico learned upon reaching Tartarus was that he would find no help from his father. The initial reaction he got from Hades was one of disappointment. Nico wasn't Bianca – and that was all that seemed to matter to the God of the Dead. Hades largely ignored his son, and Persephone looked down her nose at him. He guessed that made sense, since it meant that her husband had gone off with some mortal woman, but that didn't really help him much.
Hades' constant dismissal of him as unworthy and untalented only served to fuel his hatred for Percy Jackson. If Percy hadn't broken his promise, Bianca wouldn't have died. If Bianca were alive, Hades wouldn't be constantly lamenting that Nico wasn't her – and Nico wouldn't be so alone.

He resolved to ruin Percy Jackson the way he and Bianca had been ruined...and he resolved to earn his father's acknowledgment and approval at the same time.

He didn't anticipate how difficult either of those things would be. In the end, he was just a kid – and a kid who was way out of touch with the world. There wasn't much help to be found in Tartarus, either. His father certainly didn't want to teach him anything, Persephone wouldn't look at him, and most of the monsters would just as soon eat him as they would help him.

As for the spirits of humans in the Underworld, they rarely interacted with anything but each other – and the ones in the Fields of Asphodel didn't even really do that. They were all stuck in their own purgatorial worlds, with very little way to break through. Nico didn't really care about that, anyway; all he wanted to do was find his sister. It was almost a relief that she wasn't among the souls trapped in the Fields, but it made her harder to find. Try as he might, he couldn't seem to find Bianca anywhere. When he chanced asking Hades about her whereabouts, Hades told him that the dead stayed dead, and didn't he think if there was a way to retrieve her that Hades would have done it himself?

Nico learned quickly enough that asking Hades to teach him or tell him anything was a waste of time.

He also learned that Elysium was off limits to him, as a living person. That wasn't to say he couldn't get there. It was just that the moment he did, some kind of otherworldly alarm would alert his father. He tried three different times, each time entering Elysium a different way, and each time getting intercepted by Hades.

The third time, Hades threw him in a cell for several days. Try as he might, even with the power to move around Tartarus freely, he could not escape.

"If you think you deserve some special privileges because you have my blood, you are sorely mistaken. Do not test my patience again," Hades warned, when he finally set him free.

Nico left Tartarus after that. He didn't have anywhere to go, but he couldn't just stay in the underworld and get no answers. Anyway, he had some revenge to get, didn't he?

It was really by chance that he met King Minos. He'd read about the labyrinth in his father's library, but he hadn't expected to find it. Even with all he'd seen, the idea of Daedalus' labyrinth stretching all over like it did was hard to grasp. But it was there, just as he'd read.

And it was full of ghosts, among other things.

Since Bianca had died, nothing scared Nico. Ghosts didn't even try to scare him – not once he realized that with a word, he could bend them to his will. Not all of them, certainly not at first. But he did have an uncanny ability to get the dead to do what he wanted them to do. He wondered if his father knew about that.

King Minos was one ghost he couldn't get to do much of anything by exerting will over him...but King Minos listened to him. He listened to the story of the son of Poseidon who had gotten Bianca killed. He listened to the story of how Hades thought of Nico only as inferior to his sister. He listened to how Nico had been trying and trying to find Bianca's spirit and had been unable to.

And then, he offered his assistance. Of course, Nico didn't quite trust him, because Nico was sure he couldn't trust anyone. He'd trusted Percy, after all, and so had Bianca. And where had that gotten them? And he'd trusted Artemis to take care of her hunters, but she had failed him, too. Minos was helpful, but Nico was jaded. Still, if they could work together, then why not? It wasn't as if Nico had anything else to lose.

Under Minos's tutelage, Nico learned more about the spirits of the dead than he'd have learned in a year in his father's library. Maybe with Hades' help, he'd have learned, but on his own...he couldn't possibly have discovered the things that Minos taught him.

There were times, though, that Nico wondered if he was really doing the right thing. The thing he cared about most was getting Bianca back, after all. Minos seemed to be driving him, using him to do something, but he decided he didn't care. Nico wasn't stupid, but he was very young, and blinded by his emotions. Try as he might, though, he couldn't find Bianca – or he couldn't make her answer him, maybe. He tried everything Minos suggested, and even came up with ideas of his own. It seemed he could summon any ghost in the underworld except hers.

Finally, Minos told him that they could trade a life for hers – bring her back to life for good. Nico threw any mistrust he had for the ghost king after that, seeking only to bring his sister back. Then, he could get his revenge on Percy, and he could win his father's approval. It didn't matter what Minos wanted, in the end.

Minos, for his part, didn't stay around every moment. Nico wasn't entirely sure where he went, but maybe even ghosts had schedules. He didn't care, so long as Minos was there when he needed guidance. But the more Minos stayed away, the more Nico realized the extent of the powers his father's blood granted him. Other ghosts bent to his will. He could send them back to the underworld with hardly any thought. The more he did it, the easier it got – and he began to realize that Minos was not any match for him. The ghost had power built up after so many years of just existing, and he was a malevolent creature. But Nico had Hades' blood on his side – and all the drive and resolve of the very young.

Minos claimed to be the King of Ghosts, but that was just bravado.

It took awhile for Nico to realize that - to realize that the voice constantly chattering in his ear was playing him. Still, he allowed it to continue. He knew Minos was full of trickery, and he knew that he had the disadvantage of lack of experience. And, ultimately, he was alone. Maybe Minos wasn't great company, but he was some kind of company. Nico was still very young, and having someone who at least encouraged him was preferable to the alternative - loneliness, and disdain from his father.

In the end, he knew he would have to give it up, though. Once he brought Bianca back, he would have only a small window to get rid of Minos before Minos got rid of him.

Then he'd be the King of Ghosts. Maybe his father would see worth in him then.