The Eridians are an ancient alien race originating from Nekrotafeyo. 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 them. The entire population of their homeworld, Nekrotafeyo, willingly acted as bait to lure The Destroyer into the Great Vault. They were subsequently sealed within by an ancient Siren, whose chronicles of the event can be found scattered over planets with an Eridian presence.
The Eridians were the first ever recorded species to have lived on Pandora. They knew how to use Eridium to create technology far beyond that of humans. Eridian items can be found scattered across Pandora. Eridian weapons require no ammunition and indicate just how advanced their technology was.
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.
Although the Eridian civilization was destroyed, Eridian ruins can be found in several locations on Pandora. These ruins always contain large stones that have visible lines running through them as an identifying feature. Large broken archways can be found as well. In some areas (notably The Vault, Vault of the Warrior, and The Leviathan's Lair), there are huge ancient statues that depict Eridians. Guardians are still active in parts of these ruins and will attack on sight.
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.
- Ancient Eridian technology is a large part of the Borderlands storyline.