All the Weyrs of Pern

For generations, the dragonriders had dedicated their lives to fighting Thread, the dreaded spores that periodically rained from the sky to ravage the land. On the backs of their magnificent telepathic dragons they flew to flame the deadly stuff out of the air before it could reach the planet's surface. But the greatest dream of the dragonriders was to find a way to eradicate Thread completely, so that never again would their beloved Pern be threatened with destruction.