Eridium, not to be confused with iridium, is a new element found in Borderlands 2. It was released onto Pandora after the Vault Hunters opened 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.
Eridians and Eridium
Eridium is appropriately named after the ancient precursor race that utilized it, the Eridians. The ore has some semblance of usage as a universal power source, as the Eridian Weapons from Borderlands use Eridium chunks as a reusable and rechargeable ammunition source. Neither the Eridians nor their weapons are present in Borderlands 2, although there are a few Relics of Eridian origin.
Eridium and Sirens
Due to the mysterious relationship of Sirens to Eridians, Sirens can absorb Eridium as a means to enhance their powers. However, this has serious side effects. While Eridium increases a Siren's powers and makes them more powerful, even increasing their natural healing to the point of superhuman regeneration, the 'high' of the power boost has the potential to be addictive. Sirens that are given, willingly or forcefully, a constant flow of Eridium to absorb become unable to live without it: the Eridium essentially becomes their life support. Should the constant flow of Eridium stop, the Siren will die.
Despite this, Angel mentions in an ECHO recording that Maya (the only playable Siren in Borderlands 2) has no connection to Eridium.
The maximum number of Eridium bars a player can have at any one time is 500.
In game, Eridium can have many different uses:
- Buying character upgrades at the Black Market. These include Bank, Backpack, and Ammunition SDUs. See Black Market page for further details.
- Accessing Terramorphous Peak for fighting Terramorphous the Invincible, costs 8 Eridium for each access.
- Fighting Hyperius the Invincible, Master Gee the Invincible, Pete the Invincible and Voracidous the Invincible, costs 8 for each fight.
- Spawning Dexiduous the Invincible in Hunter's Grotto, costs 21-27 Eridium to activate each of the four shrines.
- Accessing The Winged Storm for fighting Ancient Dragons of Destruction, costs 20 Eridium for each access.
- Playing Tiny Tina's Lootsplosion Slot Machines in Flamerock Refuge, costs 2 Eridium for each pull.
- In Tiny Tina's Assault on Dragon Keep activating shrines for a short duration combat buff costs 2 for each activation.
- Using two dice instead of one when opening Dice Chests, costs 5 Eridium.
- At the end of A Game of Games, a Vault Hunter must feed Butt Stallion 5 Eridium to continue the mission.
- After finishing A Game of Games, feeding Butt Stallion in Flamerock Refuge will cause her to dispense an item in return, with a chance of producing a Gemstone weapon. It costs 5 Eridium for each interaction.
Eridium itself is also used as a powerful fuel source, however its method of production and full properties are unknown. While it seems to be almost like energy made solid, refined Eridium ore is formed into ingots. Eridium can also be used in weaponry, found in the form of E-tech gear possessing unique projectiles and improved elemental abilities.
Eridium is an uncommon-rare drop from regular enemies and rarely found in containers like lockers and chests. Some bosses drop Eridium more frequently. It can also be obtained by playing slot machines around Pandora, or as a mission reward.
Early in the story missions, if the game is saved and quit after entering Bloodshot Stronghold, an exit back to Three Horns - Divide will spawn Bad Maw again for a high chance at getting 1-4 Eridium. Later in the story missions BNK3R and the Warrior drop high quantities of Eridium. In DLCs the Handsome Sorcerer, Handsome Dragon, and the Ancient Dragons of Destruction can all drop high quantities of Eridium, with the Dragons regularly providing the most.
- Using the Tiny Tina's Lootsplosion Slot Machine provides another means of obtaining Eridium, most efficiently with four players as each one gained goes to every player present. In single player however, the expected value is still negative. The slot machines will provide approximately a 3:1 transfer rate.
In Borderlands 3, Eridium is still a rare resource. However, veins of Eridium can be found in the environment across all worlds. They are impervious to all forms of damage, and Vault Hunters will remark about not being able to break these crystals if they attempt to melee it. They require a sufficiently powerful tool to break them into useful chunks, and once broken, they provide a total of 2-4 Eridium based on the size of the vein. The Vault Hunter will gain the ability to break the Eridium crystals after acquiring the Eridian Resonator.
In addition to the chunks of Eridium, there are Eridian-themed chests that are coated in the purple crystals. These can only be broken by a sufficiently powerful tool, and take two strikes from it to free the chest. These crystals will produce a total of 4-6 Eridium. The chests are otherwise equivalent in function to white chests that can be found elsewhere in the world.
Anointed enemies are those that have been supercharged with Eridium by Troy Calypso. Anointed enemies have gained strange powers, allowing them to teleport rapidly and use elemental attacks that no other enemy could use. These enemies, when killed, do not die in a normal fashion. Instead, they will crystallize into solid Eridium. Vault Hunters can loot these giant Eridium statues for the enemy's drops using the same tool that they use for all other Eridium crystals.
In Borderlands 3, Eridium is no longer used for purchasing SDU upgrades. They are now used to:
- Purchase cosmetics, weapon skins, and room decorations from Crazy Earl aboard Sanctuary III.
- Purchase Anointed weapons from Crazy Earl's vending machine.
- Play the Vault Line slot machine at Moxxi's Bar aboard Sanctuary III for 10 Eridium.
- Pay Typhon DeLeon to fire the Eridian Fabricator.
- Fire the Eridian Fabricator for 10 Eridium (normal mode) or 250 Eridium (legendary mode).