Tommy Graves had one night to find shelter, or the cold in Darklung would freeze him in his sleep. He was twelve, small and pale, with black hair hanging over his eyes. Men in gray suits had killed his family and dumped him in this world of purple crystals and dead trees. He wanted one thing now: a friend, and a place to call his own. But first he needed a roof, and the light was already dying. He hugged his black hoodie tight and walked. His breath came out in clouds. His tennis shoes soaked through in the frost. The cold bit his fingers until he curled them inside his sleeves. He had a small pocket knife, but a knife could not stop the freezing dark. Then he saw it. A treehouse grew inside a giant dead willow. Purple crystals glittered along its walls. Broken glass gaped in the windows, and moss hung from the crooked roof. It looked spooky. It also looked like walls, and walls meant warmth. Tommy climbed the twisting roots. He pushed the old door. It groaned open. Inside, something glowed. A small girl sat in the corner. Her skin shone bright yellow-white, like a lamp. Four red eyes blinked at him. Purple and blue braids fell past her shoulders, tied with tiny amethysts. Thin tentacles curled where her arms should be. She flinched back and pulled her knees close. Tommy froze. His hand went to his knife. His heart slammed. "Please don't hurt me," the girl whispered. Her voice shook. "I found it empty. I'll go." She started to rise. Her light trembled. She looked as scared as he felt. Tommy let go of the knife. His shoulders dropped. "No," he said. His own voice cracked. "You don't have to go." She stopped. Her four eyes searched his face. "I'm Tommy," he said. "I just need somewhere warm. I won't touch anything." "Lumina," she said softly. "Lumina Starwhisper." She sat back down, but she watched him. Tommy stepped inside and shut the door against the wind. He sat far from her, back to the wall. The floor was cold. He shivered hard. Lumina looked at him for a long moment. Then she scooted closer, just a little. Her glow spread warmth across the small room. It touched Tommy's frozen hands. He held them out toward her light without thinking. "You're cold," she said. "Yeah," he said. She moved nearer still, until her light wrapped around them both. The freezing dark stayed outside. For the first time since the men took his family, Tommy was not alone. He stopped shivering. His eyes grew heavy. Then, below the treehouse, something heavy scraped against the roots. Slow. Deliberate. Circling. Lumina's light snapped bright with fear. "That comes every night," she whispered. "That's why the last ones left."

The scraping came closer. Tommy pressed his ear to the floor and heard claws bite into the willow's bark. The thing was climbing. He stared at the door. It had no lock, no bar, nothing to keep the creature out. Tonight it would reach them. "It can't get in, can it?" Tommy whispered. Lumina's four eyes dimmed with fear. "It always could," she said. "The others just ran before it tried." Tommy's chest went tight. He would not run. This place was his now, and hers too. He grabbed his pocket knife, then looked at it and felt sick. A knife that small could do nothing. He scanned the dark room. Moss. Broken glass. Then, in the far corner, a shape leaned against the wall under a fallen board. Something long. Something bright. Tommy crawled to it and pulled the board away. A sword lay there, taller than he was. The blade shone clear like diamond. Purple gems crowned the handle. Even in the dark it caught Lumina's glow and threw light across the room. "I've never touched it," Lumina said. "It's too big for me." Tommy wrapped both hands around the grip and dragged. The sword was heavy, but it moved. He hauled it to the door and stood it point-down, waiting. Wood splintered below. The whole treehouse shook. A leg came through the window first, black and furred, thick as Tommy's arm. Purple crystals studded it like barnacles. Then the head rose over the sill. Eight eyes. One glowed green. The spider forced its bulk through the frame. Lumina screamed and pressed to the wall. Her light flared white. Tommy lifted the sword. His arms shook under the weight. The spider lunged. He swung with everything he had. The bright blade struck the creature's front leg and sheared clean through. The spider shrieked. It reared back, and its wound smoked where the diamond edge had cut. It did not like the sword. It did not like the light. "The blade hurts it!" Tommy shouted. "Lumina, shine!" Lumina understood. She threw both tentacles wide and blazed as bright as she could. The room turned to noon. The spider flinched from her glow, and Tommy drove the point at its green eye. The blade sank in. The spider screamed once more, wrenched free, and dropped back through the window into the dark. Its heavy body crashed down through the branches and thudded on the ground. The scraping stopped. The night went quiet. Tommy fell to his knees, the sword across his lap. His arms burned. Lumina crawled to him and rested a tentacle on his shoulder. "You made it leave," she said. "It'll heal," Tommy said, breathing hard. "It'll come back. But now we have this." He looked at the glowing blade. "And it's afraid of your light." Below the tree, something wounded dragged itself away into the cold, leaving a wide trail in the frost that led somewhere they could not see.

Morning came gray and colder than before. Tommy woke with his fingers numb inside his sleeves. Lumina lay curled beside him, her glow dimmed to a weak flicker. Frost coated the treehouse walls. He touched her shoulder and she barely stirred. The cold was winning. One more night like the last would freeze them both in their sleep. "We can't stay here," Tommy said. His breath came out white. "There's no fire. No way to make one that lasts." He looked at the broken window where the spider had climbed. "And it knows where we are." Lumina sat up slowly. "I saw a mountain once, before I found this place. Full of caves." She pointed a tentacle toward the far hills. "Big enough to block the wind." Tommy pulled the diamond sword onto his back and helped her down the tree. The frost trail from the wounded spider still cut across the ground, leading the other way. Good. They walked toward the mountain instead. It rose ahead of them, a wall of purple crystal veined with thorny black trees. Caves opened in its face like dark mouths. Amethyst Hollow Peak, Lumina called it. Along the path Tommy gathered fallen branches, snapping them to length and tying them with a strip torn from his hoodie. His arms shook from the weight, but a stack of dry wood meant a fire that would burn. A growl stopped him cold. A black dog stepped from behind a thorn tree. Its eyes glowed purple. Its teeth were too big for its jaw, white and sharp. Lumina shrank behind Tommy. He gripped the sword, but his hands were full of firewood and he couldn't lift it fast enough. The dog lowered its head. Then it whined. It limped closer, and Tommy saw the frost matted in its fur, the ribs pushing through its side. It was starving. It was cold, same as them. Tommy set down the wood. Slowly, he pulled the last strip of dried meat from his pocket and held it out. "Here," he whispered. "It's okay." The dog sniffed his hand. Then it ate, gentle for such big teeth. Its tail moved once. Lumina laughed, a small sound she hadn't made before. The dog pressed its warm body against Tommy's leg, and for the first time in days he felt heat. They climbed into the nearest cave together. The dog led, nose low, choosing a dry hollow deep enough to block the wind. Tommy stacked his firewood and struck sparks with his knife against a stone until the kindling caught. Flame bloomed. Light and warmth filled the cave. Lumina held her tentacles to the fire. The dog curled between them, guarding the entrance, ears up. Tommy leaned back against the crystal wall. Warm at last. Safe, for now. But the fire cast their shadows huge on the cave walls, and somewhere deeper in the mountain, something else had seen the light.

The fire had burned to coals by morning. Tommy woke to a hollow ache in his belly. Lumina lay beside him, her glow thin and gray. The dog lifted its head and whined, ribs still sharp under its black fur. They had eaten the last scrap of meat the day before. Tommy knew the truth. If he didn't find food, none of them would last another day. "I have to go out," Tommy said. He pulled the diamond sword onto his back. "There has to be something to eat on this mountain." Lumina caught his sleeve with a tentacle. "Don't go far. The light hurts my eyes when I'm this weak. I can't fight the spider like before." Her four red eyes dimmed. "Come back." Tommy nodded. The dog rose and followed him out. Cold air bit his face. They climbed a narrow ledge, and Tommy's heart lifted. A tall turquoise tree grew from a crack in the crystal. Amethysts hung in its branches. Fat purple fruits swung between the leaves, striped with black. Mushrooms clustered at its roots. The dog sniffed the base and barked once. Tommy stripped a fruit and bit it. Sweet juice ran down his chin. Food. Real food. He tore off more and stuffed them into his hoodie pocket, laughing for the first time in days. He filled both arms. Then the dog growled low. Tommy turned. Four figures climbed the ledge below him. Three wore long black coats and moved as one, faces hard and matching. Tommy knew them at once. They had followed the man who killed his family. Behind them walked that man himself, gray-skinned, purple braids swaying, a ray gun in his hand. His dead eyes fixed on Tommy. "There you are, boy," Victrum Mortus said. His voice was flat and cold. "We don't leave loose ends." Tommy's arms were full of fruit. He couldn't reach the sword. The dog lunged, snarling, and one of the coated men swung his boot. The dog yelped and rolled. Mortus raised the ray gun. A green bolt cracked against the crystal beside Tommy's head. Chips flew. Tommy dropped, scrambled behind the tree trunk, and the fruit spilled around him. He grabbed what he could and ran. He pounded back down the ledge, dog at his heels. Behind him the men shouted. Another bolt scorched the ground. Tommy dove into the cave and pressed against the wall, chest heaving. Lumina stared at the fruit in his hands. "You found food." "They found us," Tommy gasped. "The man in the suit. The one who dumped me here. He's on the mountain. He came to finish it." He dropped the fruit at her feet. She ate, and her glow brightened. The dog stood guard at the mouth of the cave, teeth bared toward the ledge. Tommy pulled the sword free and faced the entrance. They had food now. But the men who killed his family were climbing toward them, and there was nowhere left to run.