Lifelines ending felt the same at the age of fifteen as it did the very first time.

As soon as they had found themselves consigned to the shores of Tartarus, Nico had known exactly what they were walking into. It wasn't something he spoke about (how could you bring up such a thing in a casual conversation?), but he could feel the throbbing, humming, pulsing life that encompassed them. He knew what the ground was made of beyond the glass shards and needles, the sand that cut through their palms, the air that ate through their lungs, the jagged rocks they climbed down or over or across slicing into their skin and sipping at their blood. Nico didn't mutter of such things because having your paternal lineage defined by Hades automatically stamped you as a permanent social pariah, but physically feeling death— for coming or in progress? Well that was a whole other level of freak and Nico di Angelo received quite enough condescending or fearful looks without giving anyone a real reason.

Camp Half Blood hadn't been his home— and neither had New Rome— but he didn't want to be chased out with the campers following on his heels, torches clutched in their hands ready to burn him like a witch during the trials. Nico needed somewhere anchored to the world of the living he could return from his longer and longer stints in his father's kingdom. But… No. Death didn't sit well with your average person, heck, even with the average demigod. After all, they all spent a good portion of their childhood fighting an early death just for the chance to grow up. Having the ability to feel when a hero was getting a few steps too close, or when their wound was in fact too severe even for ambrosia…

Nico knew without wanting to know, just like he could feel the way forward.

Everything about Tartarus was wrong and while he had spent months in his father's domain surrounded by ghouls and spirits and all kinds, death hadn't felt the same as it did in the pit. Death was definite, it was settled. Permanent. The ghosts might not like it but eventually they accepted it, settling like the foundations of old buildings because they weren't going anywhere and there was little to do about it (beyond the occasional give or groan). Without a connection to the land above they soon forgot much of their previous lives or deeds— after all, there wasn't any reason to remember in the depths of the Underworld, and there was even less to trigger any kind of nostalgia. Real heroes, of course, faired different fates— they may always remember— but getting them to keep their attention (it wafted away like vapour on a breeze) and focus to bestow a tale or a meaning was a skill the Ghost King had taken months to learn while exploring the full extent of his abilities.

They were very definitely, certainly, acceptably dead.

But in Tartarus, it felt different. These were lifelines of monsters, not men. Even after they ended they never really ceased or settled; they were toxic in the air stirring chemical storms in the atmosphere and cyclones on the ground. They caused the air to become thicker and choke the demigods— thank the gods Percy didn't know what he was breathing in. When they settled, if you could call it settling, many of them were like pushing forth from the ground growing skyward from below, hard shells protecting the evils beneath. These were different than the soft pockets growing in the flatlands he and Percy crossed with the help of Bob the Titan.

He felt every difference and without words, it was clear that Bob did, too. Neither of them mentioned anything about what the terrible terrain really signified to Percy, though they shared the occasional knowing glance. Why split hairs? The journey ahead was trying enough battling his spirits to find the will to move forward and being a little blind or oblivious— it might help. Sometimes being in the dark was better than knowing. Nico knew that first hand better than most. Once you knew something you couldn't unknown it, no matter how much you wished you could. So this was something that the older demigod didn't need to know.

So it was that Nico was eschew when it came to mentioning that on top of being exhausted, cut off from Percy's friends, travelling through a demigod deathtrap, time clenching at his heart and twisting painfully, there was also the ineffable vertigo and the stomach churning migraine from the evil atmosphere. Literally evil.

It was weighing the teen down, but he kept his head up and his mouth shut as they trudged on. Occasionally he would pause to be sick off to the side, the friendly Titan would pat his back with a massive hand nearly knocking him over. Nico would stand, wipe his mouth, and continue forward. Bob kept up light hearted chattered even if the son of the sea was too busy staring holes in the back of his skull, wishing him bodily harm, and giving him the cold shoulder.

Fuck you, Percy Jackson. He thought to himself. Not that I'm doing this for you.

Occasionally, even he had to revert to his age and roll his eyes in impatience. Percy Jackson might be courageous and heroic and brave and selfless but sometimes the younger man had to wonder how much of the salt water the son of Poseidon loved so much actually filled his head. Like, really, was there even room for a brain up there?

In a way, he was suffocating. Not just on the fumes of Tartarus (which was suffocating on monsters and really Nico could think of few things more disgusting), but from the virulent troposphere weighing in around him. It was literally sucking the life from the son of Hades and he suspected as a repeat customer, it was happening faster to himself than it was to Percy. After all, he had an unbreakable tie to the Underworld and to Tartarus after his last visit. Nico shook the thought away.

When they were jumped by a herd of telkhines, the three companions had fought their way out. It was an actual herd; he'd fought them before but he'd never seen so many. The numbers were too many for his brain to attempt to tally whilst he slashed his Stygian sword through their ranks trying to protect his own vulnerable form whilst protecting Percy as well. Despite his depletion, the Italian teen slashed and stomped and twirled, ripped, pushed, kicked, yelled, and killed. Telkhines fell around them and when it was over the knot in his stomach tightened and the pressure inside of his head swelled. The lifelines of monsters ended but they didn't really end, not in Tartarus, and they seethed around them unseen in the atmosphere.

Nico fell.

—

The first time he was just a child, four or five. There was a shaggy tabby who visited their apartment each evening begging for scraps of food and saucers of milk. Mama shooed the animal away the first few nights while wide brown eyes stared fogging up the window, nose pressed to the pane. A little girl stood watching as each evening the patchy tabby returned only to be shooed again and again. She would return inside and the little girl would tug on her mother's skirt and look up at her longingly. Each evening the tabby returned.

Eventually, mama laughed and gave into the persistent tabby. Soon after, the cat ventured inside and was affectionately called Chiazza on account of the rust and slate coloured patches across his pelt. It didn't help that his feet looked as if they'd been trudging through soot and his whiskers were strangely white compared to the rest of him. Nico couldn't remember how old he was, just that little Chiazza had been around since before he could remember.

Bianca cried when Chiazza did not come back three nights in a row. And on the fourth night a strange howling came in the middle of the night beneath the window. Mama would not let them see, but she whispered to the poor animal sweet soothing things. "He is sick, my loves. He's not long of this world." Nico had cried then because he could feel the moment that life slipped away and felt the lingering thereafter moments later.

Their eyes had met and his older sister wrapped her arms around him. Young as he was, he knew that she had felt the same whisper of cold up the small of her back. The lifeline had stretched long but it ran out like rope and when it ended both children sat shaking in their room. Minutes later Mama came to embrace them both, petting her children's hair. If she knew then about them, she didn't say but cuddled to their tremulous forms and pet their hair until her children quieted and eventually went back to sleep.

Nico had felt haunted for days.

Bianca had insisted that she was playing with Chiazza for weeks following. Mama smiled and nodded at first, humouring her in putting out of milk and scraps of food. When these began disappearing, his mother's countenance became haggard each evening, anticipating her daughter asking to feed their deceased pet. The last evening, she dried her hands on the pleats of her skirt when she finished the dishes and turned to Biance. "No, my love. Chiazza is dead and you cannot feed him. This play must stop. He has gone to heaven as all good things do in death."

She had run out crying but little Nico had promised not to tattle when he'd found her playing with Chiazza in their room in the middle of the night.

When they left Italy, he couldn't come with them. Mama had assumed she was sad to be leaving for America. "My angels, it will be safer. America is a wonderful place. It will be good to us." And so they'd fled from Europe, too young to be much the wiser about Stalin or Hitler.

After that, it became easier to tell them apart. Lifelines, that is. Those that were strong, those that were weak, those than began and those that concluded. It wasn't something he spoke about, not even to his sister because, Italian or English, it was indefinable. And Nico didn't want to know what it was, not really. So he played Mythomagic and idealised Percy Jackson, the first other person he met who embodied something special. But where Nico was dark, Percy was light; the naive demigod just wanted to walk along the shore, sand squishing between his toes, surf lapping at his ankles and face turned up towards the sun.

He wanted to love. Not begrudge.

Bianca died and then he knew and once you know you can't unknow something. Despite the distance, the Ghost King had known. Hers was the line so long entwined with his own, he would have recognised it anywhere, even half a world away. Nico had been asleep in the Big House, hidden up in the attic— after all, he didn't have a House of his own. Curled on a pile of blankets and pillows, cocooned away in a corner where no one would notice, he had woken in the middle of the night struggling against the bonds of blankets. Black curls were matted to his forehead and he was sticky with sweat. What breath he could get didn't satisfy his lungs. Nico hadn't been able to define it, not then, but then the other demigod children returned. Percy returned and he had felt it and Nico came to know it.

As much as he might want to, he couldn't really hate him. Not completely. Not really. Not actually. Because Nico had known even before— he had felt it coming but hadn't had words to process the feelings and he hadn't wanted to know in the first place. Now he couldn't unknow it and he couldn't hate Percy Jackson for that. Just like he couldn't unknow the reason why he could never hate Percy Jackson and his stupid awful sea green eyes.

—

"How are you feeling?"

Nico took a few more steps forward before shooting a bleak look at the other.

"I'm fine. I told you, I was just tired. The fighting…"

"Yeah yeah… it got to you. You told me that already but I'm not completely stupid, Neek."

"Don't call me that."

"Ickle Neeks? How's that instead? It's better than the Undertaker. See what I did there? But that's already taken… that's a wrestler."

"Are you sure you can't drown? Because I think you've suffered severe brain damage."

"Hah hah." Percy chuckled humourlessly but his surveying didn't stop.

Please stop looking at me. Please stop looking at me.

And of course when he turned those stupid awful green eyes were still locked right on him questioning and noticing. Whatever it was the older demi god was trying to see, he wasn't certain. Crossing his arms in front of his chest, he snorted, the air briefly unsettling the dark strands that fell across his face.

"See something you like?" Nico deflected, the snark practically dripping from his voice. The younger teen sped up his pace hoping to catch up with Bob who was scouting ahead to make sure the way was safe; Percy just chuckled once more and shook his head.

"You know, I have you figured out!"

Blood froze and the Ghost King stopped cold. Turning in his spot, he turned back to the other.

"Y-you… you do, do you?" While he attempted to sound calm and indolent, a shiver ran up his spine and his stomach became anchored to the spot.

"Yeah. And it's okay."

Swallowing hard, Nico somehow doubted that.

"I mean, it's the most shit situation in the world. You get back from Tartarus the first time only to fall back in with me of all people. After what happened to…" he can't say her name and his eyes cast to the ground. "And then with how you, you know, feel…"

Oh, fuck. Oh fuckity fuck fuck fuckless fuckwit.

"…about Annabeth…"

Wait, what?

"…being back down here with me… that's rough. But I mean, thanks, for saving her. That means a lot. And we'll get back to her okay?"

Tartarus could have swallowed him up then, rose from the ground and pulled him down further. Blinking, Nico stood still, a statue lit only by the faint glow of the river running along side them. But then life, what was left of it, animated his limbs once more. He laughed and shook his head.

"Yeah, sure."

Then they were attacked by two snake hairs women who, unlike Nico, very definitely hated Percy fucking Jackson and his stupid awful sea green eyes.