She peers up at a moon encircled by distant trees.
Be careful of sinkholes, her teachers said. Water flows through limestone, dissolves it, washes it away. Slowly, but water has all the time it needs. Finally the fragile stone bubble crumbles, collapses. The underground world is left open to the pitiless sky.
She’s lucky, the troll girl thinks. By day, she’d have found this hole full of poisonous sunlight and left only her body turned to a boulder to shield her friends. She squirms back into friendly darkness; better set warnings so no one else stumbles into the polluted area.