Eirlys Frostwhisper had six days of food left and no idea where to dig. She crouched at the lip of a salt-blue crevasse and watched her breath crust on her scarf. The Crystalwaste stretched flat and bright in every direction, a plain of frozen glass under a white sun. Somewhere beneath it lay the throne her grandmother had sung about before the exile: a seat of black ice that marked the old snow elf hold. Eirlys had crossed three provinces to find it. She had walked in circles for eleven days. She pulled the map from her coat. It was the only thing her grandmother had smuggled out, and it showed nothing but a single mark shaped like a moth. Eirlys had thought the moth was decoration. Now, kneeling on the ice, she was starting to think it was the instruction. A shadow moved across the map. She looked up. Butterflies were crossing the waste in a thin ribbon, hundreds of them, wings the color of stained glass. They should have frozen in the first breath of this air. They flew straight and low, ignoring her, ignoring the wind. Eirlys stood and followed. They led her half a day east, past ridges she had already searched, and stopped above a shallow bowl in the ice. There, half-swallowed by frost, stood a castle she had not seen from any ridge she'd climbed. Its stone was pale and its towers curved outward in the shape of wings. Butterflies clung to the walls in sleeping drifts. The great door was open a hand's width. Eirlys drew her knife. She had not come for a castle. She had come for a throne buried beneath the waste, and this thing sat on top of it like a lid. Inside, the air was warmer. The floor sloped down. She followed it past empty halls, past staircases that spiralled the wrong way, until the stone under her boots turned to black ice. She knelt and cleared the frost with her glove. Beneath her hand, carved into the ice, was the sigil her grandmother had drawn on the inside of her wrist the night she died. Eirlys pressed her palm flat against it. The ice did not answer. The throne was here. She was standing on the roof of her own hall. She sat back on her heels and counted what she had: six days of food, one knife, a map she now understood, and a castle full of sleeping butterflies between her and the ground she needed to reach. The door she had come through was hers to defend or hers to lose. Somewhere above her, the ribbon of wings was still arriving. She had found the throne. Now she had to learn who else lived on top of it.

Eirlys stayed on her knees above the sigil. She had found the throne's roof, but she could not open it. Her grandmother had never taught her the death-rite. The old woman had died with the words still in her mouth. To touch the throne without the proper rite would curse the last of her blood, and Eirlys was the last. She pulled her hand back from the ice. A sound moved behind her — not footsteps, but a soft beat, like cloth shaken out. Eirlys turned with the knife up. A butterfly elf stood in the archway. She was small, barely to Eirlys's shoulder, with pale hair and wings the color of shallow water. She held a lantern in both hands and watched the knife without flinching. Behind her, two long shapes coiled in the dark hall — dragons the size of horses, wings folded, eyes bright as coins. They did not move. They were waiting on the elf. "You came under our swarm," the butterfly elf said. "So you are hers." Her voice was even. "I am Sylphina. I kept the hall while she was gone." Eirlys lowered the knife an inch. "My grandmother." "She left me the rite," Sylphina said. "In case the blood came back." Eirlys's throat closed. She had walked eleven days in circles for this. "Then say it." Sylphina shook her head. "I cannot say it for you. I can teach you the shape. You must speak it yourself, with your own hand on the sigil. If you speak it wrong, the ice takes you." "How wrong is wrong?" "Any word out of order." Eirlys looked down at the black ice. She thought of six days of food and a door she could not defend forever. She set the knife on the floor. Sylphina knelt beside her and spoke the rite in a low voice, one phrase at a time. The words were snow elf, older than the exile. Eirlys repeated each phrase back until Sylphina nodded. They went through it three times. On the fourth, Sylphina stopped correcting her. "Now," Sylphina said. "Hand flat. Do not stop in the middle." Eirlys pressed her palm to the sigil. She spoke the rite through without breathing between the lines. The ice under her hand went warm. A seam opened around the sigil in a slow circle, wide as a well, and cold air rose from below with the smell of old stone. Eirlys pulled her hand back whole. She was not cursed. The way down was open. Sylphina stood and stepped back. The two dragons in the hall raised their heads at once. "They know the seal is broken," she said. "So does everything else that was sleeping in these walls. You have until the swarm wakes." Eirlys picked up her knife and looked into the opened dark.

Eirlys stood at the lip of the opened seam. The cold from below pulled at her coat. Behind her, the walls of the hall began to tick, the way ice ticks before it splits. Something was waking inside the stone. Sylphina backed toward the archway. "They come through the seams first. Small ones. Then larger." She lifted her lantern. The two winged dragons behind her flared their wings once and settled again, watching the walls, not Eirlys. A hand-shaped bulge pressed out of the wall to Eirlys's left. The stone stretched like wet cloth. A thin claw pushed through and scraped at the air. Eirlys stepped back from it and raised her knife. The knife was six inches long. The claw was longer. A second bulge opened near the floor. A third above the arch. Eirlys counted four before she stopped counting. She could not fight through this and climb down. She would die on the stair. The front doors of the hall boomed. Once. Twice. On the third strike they broke inward, and a white wolf came through the gap at a run. A man rode her low against the neck. His wings folded tight to his back. He carried a short spear. "Down," he said to Eirlys. She dropped. The wolf hit the wall where the first claw had come through. Her shoulder cracked the stone and the claw went with it. The rider pushed off her back, opened his wings once, and drove the spear into the second bulge before it finished forming. He landed on the wolf again without looking. "Sylphina," he said. "You called." "I called," Sylphina said. Eirlys stared at him. "Who." "Lysander. This is Skein." He did not look at Eirlys. He looked at the walls. "How deep is the stair." "I don't know," Eirlys said. "Go find out. We hold the hall." "Why." He struck a third bulge without answering. Skein tore a fourth open at the floor and shook the thing inside until it stopped moving. Sylphina spoke over the noise. "His people's migration is broken. Something in these walls broke it. He wants what's under the ice as much as you do." "Not the throne," Lysander said. "What sleeps around it. Go." Eirlys did not thank him. She swung her legs into the seam and lowered herself onto the first step. The stair went down into black air that smelled of old stone and older cold. Above her, the wolf snarled and the spear struck wood or bone, she could not tell which. She went down three steps and stopped. The hall behind her was noise. The dark below was silent. She had bought her way to the stair, and she had bought it with a stranger's fight she did not understand. She kept going down.