Because the Sirin view flight and musical capability as the ultimate signs of divine favor, those who cannot fly or sing are treated as property, forced to build the infrastructure that keeps the high-caste paradise afloat.
The Mine-Tethered (Dwarves and Orcs): Kept in the dark, under-mountain vaults beneath the peaks. They perform the deadliest work on the continent: mining Skystones and raw celestial silver. Because skystones naturally repel gravity, these slaves work in heavy iron boots chained to the stone floors so they do not accidentally float away into deep cavern ceilings or drift out of open mountain cracks during a cave-in. [1]
The Canopy-Bound (Elves and Tabaxi): Found in the humid depths of the Sunken Oasis. They are forced to harvest the massive iron-oak trees and rare, toxic jungle mosses used for airship construction. They work hundreds of feet up in the jungle canopy, wearing heavy leather neck-collars tethered to thick hemp ropes held by flying Sirin overseers. If a slave slips, their overseer decides whether to pull the rope or let them drop.
The Domestics (Humans and Halflings): The house-slaves of the elite quarters in Aephos. They work as cooks, cleaners, and laborers in the floating palaces. They are forced to wear The Velvet Gags—soft cloth masks woven with silence runes that prevent them from speaking or making sound while serving their masters, ensuring they do not disrupt the perfect ambient melodies of the high estates. [1]