The Sky-Whale Migration

Sky-whales aren't animals — they are condensed Aether that has gained sentience and form. They don't eat; they filter raw Aether through their bodies, and the islands float on their exhaled currents. When a whale dies, an island falls.

The whale-callers are the oldest profession in Aetheria. They stand on the edges of the islands and sing in a language that predates all human civilization — a language the whales taught them, or that humans invented to mimic the whales. No one remembers which.