Dragonquest

Rukbat, in the Sagittarian Sector, was a golden G-type star. It had five planets, two asteroid belts, and a stray planet it had attracted and held in recent millennia. When men first settled on Rukbat's third world and called it Pern, they had taken little notice of the stranger planet, swinging around its adopted primary in a wildly erratic elliptical orbit. For two generations, the colonists gave the bright red star little thought -- until the desperate path of the wanderer brought it close to its stepsister at perihelion.

When such aspects were harmonious and not distorted by conjunctions with other planets in the system, the indigenous life of the wanderer sought to bridge the space gap to the more temperate and hospitable planet.

The initial losses the colonists suffered were staggering, and it was during the subsequent long struggle to survive and combat this menace dropping through Pern's skies like silver threads that Pern's tenuous contact with the mother planet was broken.

To control the incursions of the dreadful Threads (for the Pernese had cannibalized their transport ships early on and abandoned such technological sophistication as was irrelevant to this pastoral planet), the resourceful men embarked on a long-term plan. The first phase involved breeding a highly specialized variety of a life-form indigenous to their new world. Men and women with high empathy ratings and some innate telepathic ability were trained to use and preserve these unusual animals. The "dragons" (named for the mythical Terran beast they resembled) had two extremely useful characteristics: they could get from one place to another instantly and, after chewing a phosphine-bearing rock, they could emit a flaming gas. As the dragons could fly, they'd be able to char Thread mid-air, yet escape its worst ravages themselves. It took generations to develop to the full the use of this first phase. The second phase of the proposed defense against the spore incursions would take longer to mature. For Thread, a space-traveling mycorrhizoid spore, devoured organic matter with mindless voracity and, once grounded, burrowed and proliferated with terrifying speed.

The originators of the two-stage defense program did not compensate sufficiently for chance nor for the psychological effect of visible extermination of this avid foe. For it was psychologically reassuring and deeply satisfying to the endangered Pernese to see the menace charred to impotence in mid-air. Also, the southern continent, where the second phase was initiated, proved untenable and the entire colony was moved to the northern continent to seek refuge from the Threads in the natural caves of the northern mountain ranges. The significance of the southern hemisphere lost meaning in the immediate struggle to establish new settlements in the north. Recollections of Earth receded further from Pernese history with each successive generation until memory of their origins degenerated past legend or myth and into oblivion.