Dragonflight

Pern is a planet colonised by humans. The original colonists originally intended to adopt a low-technology agrarian lifestyle gradually, but were thrust into this more precipitously after they encountered the onslaught of the deadly Thread raining down from the sky. By harnessing the indigenous flying, fire-breathing dragons (with genetic alterations to make them larger and telepathic), the dragons, with their human riders, destroyed the Thread in the skies over Pern before it was able to burrow into the land and breed, creating pockets of safety over Pern's surface