“Saying how sorry I am will never make up for what has been done to you,” I said. “This is barbaric.”

“I have deserved no less a fate,” the Naphil said. “I have done murder, Gabriel, and you imprisoned a criminal. That is the difference between our sins.”

“Then you understand why I must kill you now?” I asked him.

“I have always known that you would come for me one day and why,” he said. “I’ve had thousands of years to accept that I have done evil and that this is my punishment. I welcome death. Tell me about these beasts, the demonic reapers.”

“They have gathered against us and are killing as many humans as they can and sending their souls to Hell. We can’t let them do this anymore. We have to stop them once and for all. Sammael and Lilith, the Fallen leading the demonic, want to annihilate all life, everything.”

The Naphil tried to stand, but his muscles had clearly atrophied. He slumped back over and his head lolled about on his shoulders. He stared sadly at the ground. “I am tired,” the Naphil said. “I am tired of this hole in the earth.”

“I wish I could offer you a better fate,” I told him. I wanted nothing more than to free him and let him see the sky again, feel the sun on his skin, to let him live. But I couldn’t. He couldn’t live, and neither could I. I once asked myself if I could sacrifice others to win this war, and now that I knew I could answer that question with a ‘yes,’ I hated myself.

The Naphil’s pitiful gaze found mine. “Kill to save many lives, Gabriel. Begin with me. Give me an honorable death.”

“I’m sorry for what I have to do,” I said.

“Do not be sorry for this,” he said. “This is mercy. I do not want to live like this anymore. Whatever fate greets my soul after death must be better than the weight of old iron chains.”

Will stepped forward. “I’ll do it, Ellie. Don’t—”

“No,” I said firmly. “I did this to him. I have to finish it.”

The Naphil watched me as I moved toward him and called a single sword into my hand.

I would never forget the feel of the Naphil’s skin breaking under the metal of my sword. I forced myself to watch him die as his life’s blood poured from his haggard body. His eyes only left mine when he was gone. I wrapped his heart, which was about the size of a basketball, with linen that Rebekah gave me, and tucked it into my backpack.

The moment we left the Sanctum, the torches went out and the chamber turned to blackness, swallowing the corpse of the Naphil. We started back the way we had come and explored several tunnels that each ended in a wall of stone or another cave-in. Rebekah and Ethan walked well ahead of Will and me, poking at a tunnel system map between them.

“Derinkuyu had a ventilation shaft that was also used as a well,” Dr. Massi said excitedly. “Most ventilation shafts are too tight for any of us to fit through, but one through which water is drawn should be wide enough. We may be able to use it to escape.”

She hurried off, ducking into tiny doorways and whirling around columns, and the trickling sounds I’d heard since we entered the city grew louder as we followed her. The passage became a staircase that took us up and then back down again until it opened into a large cavern filled with water that gave off an eerie azure glow. The ceiling was two stories high at least and at the apex, a beam of daylight shone through a well shaft and hit the water.

“Oh, excellent,” Ethan Stone said. “A way out. Good thing I was sure to be bitten by a radioactive spider so I can scale these walls and ceiling and shimmy my arse right out of here.”

Will studied the well shaft for a long moment. “I don’t think that would work,” he murmured as Ethan’s bad joke went right over his head. “I could fly up there. It’s too narrow to fly all the way up, but I could climb. If I’m out, then I can find a rope, or look for another exit.”

I nodded. “Good thinking. Maybe we can be out of here by dinnertime. I’m starved.”

He shrugged off his T-shirt and handed it to me so I could keep it in my pack. He stepped over to the edge of the water and his wings spread with a slow grace to their full sixteen-foot breadth. Rebekah drew a sharp breath and whimpered, but she managed to hang on to her composure. Will jumped into the air, his wings beating a cloud of dust off the ground, and he rose through the center of the slant of golden sunlight. It only took him a single powerful wing-stroke to reach the shaft. His hands dug into grooves in the rock and he pulled his body into the narrow tunnel, the muscles in his arms and back twisting and straining with strength. His wings re-formed into his skin and his boots kicked into rock to push himself higher until he was out of my sight. My gut tightened for several long minutes as he scaled the well shaft and I held my breath when I couldn’t hear him anymore.

Then something tumbled through the shaft, banging on rock, and a bucket tied at the end of a rope appeared and splashed into the water.

“Ellie!” Will’s voice called from the surface. “Ellie, get the others to swim to the bucket and hang on. It should be strong enough to hold the weight while I hoist you all out one by one.”

“There must be an active village built around this well,” Rebekah said.

I dipped my fingers into the water to test the temperature. It was surprisingly chilly, but we’d warm up once we got to the surface and into the sunlight. “You two go first,” I instructed.