In the world of Aethelgard, fragments of a shattered moon, known as "Shardfall," rain down periodically, each piece containing latent, volatile magic. The Sky Wardens, an ancient order of mages sworn to protect the realms, use this magic to build and sustain the flying city of Aerthos. Their power is waning, and the fragments are falling faster and becoming more dangerous, threatening to destroy the world below. The story follows Lyra, a disgraced former Warden, who discovers that the Shardfall is not a natural disaster but the result of a forgotten celestial being trapped in the moon's core. She must journey to the world below, a place the Wardens abandoned centuries ago, to find the means to stop the falls and save both the sky and surface realms.