The Dragonriders of Pern is a series of science fiction stories written primarily by Anne McCaffrey. The purpose of the game is for the player to battle Thread and engage in diplomacy on Pern. Pernese people are described as belonging to four basic groups: Weyrfolk (including Dragonriders) who live in the Weyrs, the Holders who live in the Holds (cities, towns and farms), the crafters who live in Crafthalls (or are assigned to work their crafts in certain Holds), and the Holdless who have no permanent home (including traders, displaced Holders, and brigands). One of the main threats to Pernese civilization in the series is Thread, which is described as a mycorrhizoid spore that periodically rains down on the planet due to the orbit of the Red Star.