prologue

In darkness, not all was invisible. Not all was silent. Contrary, shadows ghosted past and sounds ripped through the air — tortured cries, souls being gouged from their roots, heavy sighs, final, hopeless breaths. The stillness of it all was the most painful. Quiet, but sucking, like a vacuum, the life force and spirit, the vitality and energy. The cold hit like a thousand knives, whittling straight to the bone, drying out all warmth.

It didn't feel like falling. There was no sense of panic, or adrenaline. It was pure oppression. There was no sickening lurch of gravity in the pits of the stomach. There was just hollowness.

There was no way to describe the sensation of having your life force ripped from its foundations. It was the cruelest, sickest kind of pain. Worse than suffocating. Worse than holding up the sky. A million times worse than drowning in the cursed water at the nymphaeum, back in Rome, miles above them on the surface — where the Sun was. (The sky, the greenery, the land, the sea — it was no wonder Hades had been bitter for so many eons.) This pain was cutting, it was the most raw form of fear, of emptiness, of hopelessness. It drove all rational thought out of his mind. There was only one thing he was sure of, that he'd been sure of all this time.

Annabeth. The faint, almost invisible sheen of her blonde hair in the gloom. Her hand in his, cold, clammy, her grip excruciatingly weak, but it might as well have been an energy well. It gave him strength. That hand in his was the only thing he could possibly focus on — he was with her. Nothing else mattered. This was as good as he could've hoped for.

How ironic, a snide part of him that seemed to be spluttering out its last words, said. That you're falling straight through hell, and this is what goes through your head.

There was no energy to respond, there was just enough to keep breathing. In and out, in and out. More black, frigid air filled his lungs, drying them out. Keep breathing, he told himself. And keep holding on.

And he did hold on, for eternities until he hit the hard surface of a water body, a bone—shattering impact that would've killed him, but Percy embraced the water and took ownership of it, bending it around them to cushion the fall. Air bubbles cushion a fall, he thought, employing his survival instincts. Over the churning and splash, there was no cry of shock or fear from either of them. He tightened his hold, pushing his last energy into the hand, ignoring the pain. The water wasn't still, it was fast-flowing, and it wasn't unfriendly water either — just normal, sub-zero freshwater. Willing the currents to sweep them gently ashore, Percy braced himself for the landing, and they collapsed beside the river — holding on, but barely. For a few moments — or was it a few hours, he lay still, just breathing, calming himself and letting the water ventilate to remove the suffocating sensation. He couldn't see, but he could sense Annabeth lying motionless, just next to him, on the craggy floor that resembled moon rock.

She stirred, which came to him as a shock. He realized she was stretching out her other hand to him, and his eyes followed her. She was holding two cubes in her palm — ambrosia squares.

It was as though he'd been recharged — the combination of compressed, blue chocolate chip cookies, and the healing powers of the godly food. One hand fumbled for the pen, and uncapped the sword. A faint glow emanated from the bronze blade. His eyes could focus again. He didn't have to remind himself to breathe, although he could hear his breath, and it was shallow and came in short gasps. He flexed his fingers experimentally; all his joints were mobile, but the skin was dry as leather. His back hurt, very badly as far as he could tell — but Annabeth couldn't have landed much better, and her leg had already been incapacitated.

"I didn't know that they had rivers in Tartarus," was all he could say.

Annabeth coughed twice. "Cocytus. The origin of all water," she said, and her voice was thin like an old woman's, small like a little girl's. "All rivers flow through the chasm of Tartarus."

It was a while before either of them spoke again. "Well, we're alive," Annabeth said, her voice full of false bravado.

"In Tartarus. I never thought I'd live to see the day."

She moved closer, not responding. Each movement took effort.

"Nico and the others — they'll be on there way here right now, right? You told him to meet us on the other side," she said. "Tartarus — I've studied this place for ages. I think I can navigate. But I'm not sure if my knowledge is enough. Nobody knows much about this place."

Percy squeezed her hand. "We'll find our way out. First, we've got to survive."

Slowly, they both sat up and blinked, adjusting to the dark. It wasn't all dark, Percy realized. Green flames flickered in the distance, not too far away. It reminded him slightly of the Hades cabin, back at camp. Against the wall, hulking shadows were rising and falling. He couldn't hear much from that direction, just the sound of fast—flowing water, and air, an empty echo in the endless cavern. On the wall across from them, there were a few haphazardly scribbled signs, written in Ancient Greek.

"PUNISHMENT — 200 MILES" one barely legible sign read. The engraving and bezels on the frame of the chrome had long since been leveled out. "ASPHODEL — 500 MILES". With her leg, Annabeth wasn't moving hundreds of miles in any direction. There was a third sign, circular, and hanging precariously by a single delicate filigree from the second. Percy reached forward to dust off the grime and get a better reading, but his fingers slipped and contacted with the black cavern wall. Instantly, he knew that something was wrong. The stuff he'd contacted wasn't solid — it was viscous black slime that slid like vines over his fingers without losing surface tension. His mind still unbearably hazy, Percy tried to wipe the stuff off on the signboard, but it was creeping up his arm now, and stretching across his chest. From her position at the opposite end of the tunnel, Annabeth croaked, "Is everything alright there?"

Fear seized his heart like a vice. Sweat, pure terror, beaded on his forehead. He scraped his hand desperately against the wooden sign, and the panic only heightened as the vine began winding around his neck. The world became a blur. His other hand scrabbled furiously at the plasticky goop, and the vile stuff just continued spreading on his other forearm. His sword was all the way across the cavern, out of reach. Then he heard it. A quiet voice, practically a whisper, but a powerful one. The water.

He ran towards the stream, and extended his hand along the bank. Calm swept over him, and the water crept up his arm, loosening the vines and dissolving his bonds. The black slime slid down into the stream and was carried away by the gentle current. Still, he was traumatized. Had all his capability for rational thought been eradicated?

"It's nothing," Percy said, turning around. Inside, he was shaking. "I don't think we're going to get out of here by walking, though."

Annabeth was staring at the ground, and Percy realized what she was looking at — a collection of symbols carved into the craggy rock. "This is possibly the only place in Tartarus that isn't overrun by monsters," she said. "We should be exactly at the center of Tartarus. The Doors of Death, following logic, would be situated at the deepest end."

"We aren't moving there yet," Percy said. Mrs O' Leary, he thought. "You have to recover."

"We don't know how long that'll take," Annabeth said, looking at her ankle. "This sort of injury takes weeks to heal."

"You can't battle Gaea on one foot."

"Fine."

"Got any rations?" Percy asked, not hopeful. Annabeth rummaged about in her pack, and produced a few packets of crackers, some ambrosia, water, and matches. She shook her head.

"Not much."

Percy's heart fell, but he kept his face straight as he racked his brain for possibilities. "No worries," he said falsely. "I'll just ... go scout around."

A/N: Abrupt, but what do you think?