The Eridani are a mysterious alien species in the Pern universe. They were master geneticists, and had trained Kit Ping Yung. Little is known of them, other than that they take a very long-term view, and prefer to avoid altering ecosystems if at all possible. When they do make an alteration, a sacred obligation is produced to watch it and protect it for, not only the Eridani who performed the alteration, but her bloodline for thousands of generations. They prize harmony. A good change, they say, should be invisible. It should fit, seem like an obvious part of the ecosystem.

In Dragonsblood, it is implied that the entire Pern colony was an Eridani plan to restore harmony to the Pernese ecology, in the face of the regular incursions of Thread.