The Eridians are an ancient alien race of unknown origin. Their vastly superior technology allowed them to create the Vaults and other marvels, including their weapons and relics that are scattered around Pandora.
Little is known about the Eridians, although their importance is unquestionable. What is known is that they had advanced to a technological state far superior to that of humanity and had maintained at least part of their society on Pandora. Not only did they create the Vaults, but they are also believed to be responsible for leaving the Guardians behind to protect it. It has also been determined that their entire civilization has been destroyed at some point after the creation of the Vault. Eridian ruins can be found in several locations on Pandora as a final testament to that civilization.
By reverse-engineering broken remnants of alien technology, of possibly Eridian origin, humanity made centuries of technological advances almost overnight. It also made the Atlas Corporation the most powerful company in human space, as they were the first to discover and reverse-engineer the alien technology. Their find triggered the "gold rush" of corporations to planets like Pandora and later, the tales of the Vault.
Nothing is known for certain about the physiology of the Eridians, although their statues and the Guardians carry an upright, insect-humanoid appearance, leading to the popular belief that the Eridians themselves were similar in structure. One notable trait on their creations is the presence of wings, in many cases glowing with a phosphorescent light.
According to Patricia Tannis the Eridians maintained a "class-based society which is capable of both leadership and organized warfare". She managed to determine this by translating Eridian writings found in Eridian ruins using her translation program as can be heard in one of her data recorders in Rust Commons West. It does seem that they were well versed in weapons technology and design, capable of not only creating powerful weapons and systems but near invincible bioweapons as well.
- Main article: Eridian weapons
- Main article: Artifacts
- Patricia Tannis pronounces Eridian as if it were spelled "Eridan": 'air-ih-dan', even though her speech subtitles spell it properly.