Eridium

Eridium, not to be confused with Iridium, is a new element found in Borderlands 2. It was released onto Pandora after the Vault Huntersopened The Vault in the events of Borderlands. Along with the discovery of Eridium, Slag, a by-product of refining Eridium, has been used for weapon manufacture due to its unique properties.

Eridium can be used by NPC Sirens to augment their own powers.

The maximum number of Eridium bars a player can have at any one time is 500.