In a dystopian future, humanity is plagued by the Nightmare Spell, a mysterious phenomenon that infects young people and transports them into "Nightmares"—deadly trials within a crumbling magical world known as the Dream Realm. If they survive, they become Awakened, gaining supernatural powers and the duty to protect Earth from Nightmare Creatures. Sunny (Sunless), a cynical street rat who has spent his life in the slums, is unexpectedly chosen by the Spell. While others receive heroic roles, Sunny's power—the ability to manipulate his shadow—comes with a treacherous "Flaw": he cannot tell a lie and is spiritually bound by his True Name, which makes him a "Shadow Slave" to whoever speaks it. Forced into an uneasy alliance with the brilliant Nephis and the blind seer Cassie, Sunny must navigate a world of cosmic horrors and ancient ruins while desperately trying to retain his freedom and sanity in a universe that seems determined to make him a pawn of fate.