To forestall the incursions of the dreadful Threads, the Pernese, with the ingenuity of their forgotten Terran forebears, developed a highly specialized variety of a life-form indigenous to their adopted planet. Such humans as had a high empathy rating and some innate telepathic ability were trained to use and preserve this unusual animal whose ability to teleport was of great value in the fierce struggle to keep Pern bare of Threads.
The winged, tailed, and fiery-breathed dragons (named for the Earth legend they resembled), their dragonmen, a breed apart, and the menace they battled, created a whole new group of legends and myths.
Once relieved of imminent danger, Pern settled into a more comfortable way of life. The descendants of heroes fell into disfavor, as the legends fell into disrepute.